Line of Duty Season 6: Cast, Plot, Ending, Episodes & 2026 Guide

Line of Duty season 6 is one of the most talked-about chapters of the BBC crime drama. First shown in 2021, the season follows AC-12 as Steve Arnott, Kate Fleming, and Ted Hastings investigate a controversial police officer and a case that leads back to the mysterious figure known as “H.” The six-episode season introduced DS Joanne Davidson, played by Kelly Macdonald, and built toward a major finale that finally answered one of the show’s biggest questions. In 2026, Season 6 remains essential viewing for anyone preparing for the confirmed return of Line of Duty season 7.

What Is Line of Duty Season 6?

Season 6 continues the story of AC-12, the fictional anti-corruption unit at the center of the series. This time, the investigation focuses on Detective Chief Inspector Joanne Davidson and whether her actions are connected to a wider corruption network.

• 📺 Season 6 aired in 2021.
• 🎬 It was the sixth main series.
• 🔎 AC-12 investigates police corruption.
• 👮 Steve Arnott returns.
• 👮 Kate Fleming returns.
• 🧑‍✈️ Ted Hastings returns.
• 👩‍✈️ Kelly Macdonald joins as Joanne Davidson.
• 🕵️ Davidson becomes the main investigation.
• 📋 The team examines her police work.
• 🧩 The case develops several mysteries.
• 🔎 AC-12 searches for evidence.
• 👤 The mystery of “H” continues.
• ⚠️ The investigation becomes increasingly complex.
• 📺 The season contains six episodes.
• ⭐ The finale provides major answers.
• 🌟 Season 6 remains important to the wider story.

Season 6 was created by Jed Mercurio and continued the show’s focus on police corruption, loyalty, evidence, and hidden connections.

Line of Duty Season 6 Cast

The Season 6 cast combines returning characters with several important new faces. Kelly Macdonald’s performance as Joanne Davidson became one of the biggest additions to the series.

• 👮 Martin Compston plays Steve Arnott.
• 👮 Vicky McClure plays Kate Fleming.
• 🧑‍✈️ Adrian Dunbar plays Ted Hastings.
• 👩 Kelly Macdonald plays Joanne Davidson.
• 👮 Shalom Brune-Franklin plays Chloe Bishop.
• 👮 Perry Fitzpatrick plays Terry Boyle.
• 👮 Anna Maxwell Martin plays DCS Patricia Carmichael.
• 👮 Stephen Graham plays DS John Corbett in the wider storyline.
• 👤 Nigel Boyle plays Ian Buckells.
• 👮 Gregory Piper plays Ryan Pilkington.
• 🎬 Prasanna Puwanarajah plays Nadarajah.
• 🕵️ Tommy Jessop returns as Terry Boyle.
• 📋 Returning officers continue the corruption investigation.
• 🎭 New characters create fresh suspects.
• ⭐ The ensemble keeps the series unpredictable.
• 🌟 The cast helped make Season 6 a major BBC drama.

The central trio of Steve Arnott, Kate Fleming, and Ted Hastings remained the foundation of the season, while Davidson became the main new character.

Kelly Macdonald as Joanne Davidson

Joanne Davidson is the central police officer investigated in Season 6. She is a Detective Chief Inspector leading a murder investigation, but questions about her behavior gradually bring her into AC-12’s sights.

• 👩 Kelly Macdonald plays Joanne Davidson.
• 👮 Davidson is a senior detective.
• 🔎 She leads a murder investigation.
• 📋 Her decisions attract attention.
• 🕵️ AC-12 begins examining her conduct.
• ⚠️ Her personal relationships become relevant.
• 🧩 Her background contains important secrets.
• 🔎 Steve and Kate investigate her.
• 🧑‍✈️ Hastings oversees AC-12.
• 👥 Davidson works with a large police team.
• 📺 Her storyline drives much of Season 6.
• 🎭 Macdonald gives the character a complex role.
• 🔄 The investigation changes as new evidence appears.
• 🧩 Her story connects to wider corruption questions.
• 🌟 Davidson is one of the season’s defining characters.

Her investigation creates the central mystery that carries viewers through all six episodes.

Line of Duty Season 6 Plot

The main plot begins with the murder investigation led by Joanne Davidson. AC-12 becomes interested in the case after noticing concerns surrounding her conduct and the decisions made by her team.

• 🔎 Davidson leads a major murder inquiry.
• 👮 AC-12 begins investigating her.
• 🕵️ Evidence becomes increasingly important.
• 👤 Terry Boyle remains connected to the case.
• 🧩 Earlier corruption storylines return.
• ⚠️ Several characters become possible suspects.
• 🔎 Steve investigates hidden connections.
• 👮 Kate faces difficult professional choices.
• 🧑‍✈️ Hastings faces pressure.
• 👤 Carmichael becomes important to AC-12.
• 🕵️ The “H” mystery continues.
• 📺 Each episode reveals new information.
• 🔄 Suspicions change throughout the series.
• ⚖️ Police power and accountability remain major themes.
• 🌟 The finale brings several mysteries together.

Season 6 deliberately keeps viewers guessing, using interviews, evidence, conflicting stories, and unexpected discoveries to build tension.

Line of Duty Season 6 Episodes

Season 6 contains six episodes, with the investigation developing from a relatively focused case into a much wider corruption mystery.

• 📺 Episode 1 introduces Joanne Davidson.
• 🔎 AC-12 begins looking into her case.
• 🧩 Episode 2 expands the investigation.
• 👮 Steve and Kate gather more evidence.
• ⚠️ Episode 3 increases the pressure.
• 🕵️ New information changes the investigation.
• 📋 Episode 4 reveals important connections.
• 🔎 AC-12 gets closer to the truth.
• 🧩 Episode 5 prepares the final investigation.
• 🚨 The pressure reaches a high point.
• 📺 Episode 6 delivers the main answers.
• 👤 The identity behind “H” becomes clearer.
• ⚖️ The finale examines accountability.
• ⭐ The final episode became a major television event.
• 🌟 The six-episode structure keeps the story focused.

Each episode adds another piece to the wider puzzle, making it easier to understand the season when watched from beginning to end.

Line of Duty Season 6 and AC-12

AC-12 remains central to Season 6, but the unit faces increasing pressure from senior police leadership. Its methods and effectiveness are repeatedly questioned.

• 🏢 AC-12 investigates police corruption.
• 👮 Steve is one of its key investigators.
• 👮 Kate has a long history with the unit.
• 🧑‍✈️ Hastings leads the team.
• 📋 Investigators collect evidence.
• 🔎 Police records become important.
• ⚠️ Senior officers challenge AC-12.
• 👤 Patricia Carmichael becomes significant.
• 🧩 The unit searches for “H.”
• 📺 AC-12’s future becomes uncertain.
• 🔄 Internal conflicts affect investigations.
• ⚖️ Accountability remains a major theme.
• 🕵️ Steve and Kate continue searching for answers.
• 🧑‍✈️ Hastings faces professional pressure.
• 🌟 AC-12 remains the heart of the series.

The season explores whether an anti-corruption unit can effectively investigate powerful officers when its own future is under threat.

Line of Duty Season 6 and “H”

The identity of “H” is one of the major mysteries running through the later seasons of Line of Duty. Season 6 finally provides a major answer to this long-running question.

• 🕵️ “H” is a mysterious corruption figure.
• 🔎 AC-12 has searched for the person for years.
• 🧩 Clues appear throughout the season.
• 👮 Steve continues investigating.
• 👮 Kate remains involved.
• 🧑‍✈️ Hastings wants answers.
• 📋 Police communications provide clues.
• 👤 Ian Buckells becomes increasingly important.
• 🧩 The final episodes reveal the truth.
• 📺 The reveal occurs in the Season 6 finale.
• ⚖️ The storyline changes the direction of the series.
• ⭐ It resolves one of the show’s biggest mysteries.
• 🔄 The investigation continues after the reveal.
• 🌟 The ending prepares the way for future stories.

Spoiler: The Season 6 finale reveals that Ian Buckells is the person identified as “H.” The discovery was one of the most significant moments in the entire series.

Ian Buckells in Season 6

Ian Buckells had appeared throughout the series as an officer who often seemed less important than the main suspects. Season 6 changes that perception dramatically.

• 👮 Nigel Boyle plays Ian Buckells.
• 🧑‍✈️ Buckells is a senior police officer.
• 🔎 His behavior attracts suspicion.
• 📋 His decisions become important.
• 🧩 Earlier appearances gain new meaning.
• ⚠️ AC-12 discovers important evidence.
• 🕵️ His involvement is linked to “H.”
• 🔎 The finale exposes his role.
• 📺 The reveal comes in Episode 6.
• ⭐ Buckells becomes central to the final mystery.
• ⚖️ His story raises questions about corruption.
• 🧩 The reveal changes the interpretation of earlier events.
• 🔄 The wider conspiracy remains complicated.
• 📺 His character becomes one of Season 6’s biggest surprises.

Line of Duty Season 6 Ending

The Line of Duty Season 6 ending answers the “H” question but leaves other issues open. AC-12 discovers Buckells’ involvement, while the wider corruption network is not completely eliminated.

• 🚨 The finale reveals major evidence.
• 👤 Ian Buckells is identified as “H.”
• 🔎 AC-12 learns more about the corruption network.
• 👮 Steve remains involved in the investigation.
• 👮 Kate continues her work.
• 🧑‍✈️ Hastings faces his own consequences.
• 🏢 AC-12’s future remains uncertain.
• 🧩 Some questions are answered.
• ❓ Other questions remain open.
• 🔎 The wider network is still important.
• 📋 Evidence links characters across earlier seasons.
• ⚖️ The ending focuses on accountability.
• 📺 The final episode became widely discussed.
• ⭐ The “H” reveal surprised many viewers.
• 🔄 The ending leaves room for another story.
• 🌟 Season 7 can continue from this point.

The ending is therefore not a complete conclusion to every corruption storyline. Instead, it closes one major mystery while leaving the fictional police world open for future investigations.

Line of Duty Season 6 and Ted Hastings

Ted Hastings faces one of his most difficult periods in the series. His position within AC-12 and his personal decisions become major parts of the final episodes.

• 🧑‍✈️ Adrian Dunbar plays Ted Hastings.
• 🏢 Hastings leads AC-12.
• ⚠️ He faces serious professional pressure.
• 📋 His decisions are questioned.
• 🔎 Investigators examine his actions.
• 👮 Steve remains loyal to him.
• 👮 Kate has complicated feelings about the situation.
• 🧩 Hastings’ personal history becomes relevant.
• 📺 His storyline develops across the season.
• ⚖️ Accountability becomes central.
• 🚨 His future in AC-12 becomes uncertain.
• 🧑‍✈️ He tries to protect the unit.
• 🔎 The final episodes bring his story to a major point.
• 📋 His relationship with Steve remains important.
• ⭐ Hastings remains one of the show’s most recognizable characters.
• 🌟 His Season 6 storyline helps set up future events.

Line of Duty Season 6 and Kate Fleming

Kate Fleming’s role changes significantly during Season 6. She is caught between her professional responsibilities, her relationship with AC-12, and the investigation into Davidson.

• 👮 Vicky McClure plays Kate Fleming.
• 🔎 Kate is an experienced detective.
• 🕵️ She becomes involved with Davidson’s case.
• 📋 Her professional judgment is tested.
• 👥 She works with Steve.
• ⚠️ She faces difficult choices.
• 🧩 Davidson’s behavior creates uncertainty.
• 🔎 Kate searches for evidence.
• 📺 Her relationship with AC-12 changes.
• 👮 She remains an important investigator.
• ⚖️ Loyalty is a major theme.
• 🔄 Her career direction becomes uncertain.
• 🧑‍✈️ Hastings remains part of her professional history.
• ⭐ Kate remains central to the series.
• 📺 Her decisions affect the investigation.
• 🌟 Her storyline helps connect Season 6 to the future.

Line of Duty Season 6 and Steve Arnott

Steve Arnott continues to be one of AC-12’s most determined investigators. His personal struggles also continue alongside the main corruption investigation.

• 👮 Martin Compston plays Steve Arnott.
• 🔎 Steve works for AC-12.
• 🕵️ He investigates police corruption.
• 📋 He studies evidence carefully.
• 👥 He works closely with Kate.
• 🧑‍✈️ He has a strong relationship with Hastings.
• ⚠️ His career faces pressure.
• 🧩 The “H” investigation remains important.
• 🔎 He helps uncover Buckells’ involvement.
• 📺 His storyline continues from earlier seasons.
• 👮 He remains committed to finding the truth.
• ⚖️ Professional loyalty affects his choices.
• 🔄 His relationship with AC-12 evolves.
• ⭐ He remains one of the show’s central characters.
• 📺 His role continues into the future.
• 🌟 Steve is an important link between Seasons 6 and 7.

Line of Duty Season 6 Finale Explained

The finale is designed to answer the biggest questions while leaving enough uncertainty for future stories. Its most important reveal concerns Buckells and “H.”

• 🧩 Buckells is revealed as “H.”
• 🔎 AC-12 gets a major breakthrough.
• 👤 Davidson’s story reaches its conclusion.
• 📋 Evidence explains several earlier mysteries.
• 🕵️ The corruption network becomes clearer.
• ⚠️ Not every corrupt officer is identified.
• 👮 Steve continues investigating.
• 👮 Kate’s future remains important.
• 🧑‍✈️ Hastings faces the consequences of earlier events.
• 🏢 AC-12’s future becomes uncertain.
• 📺 The final episode resolves the main case.
• ⭐ The “H” reveal closes a long-running mystery.
• 🔄 The fictional police world remains open.
• ❓ Some questions remain unanswered.
• 🎬 The finale creates possibilities for another season.
• 🌟 Season 7 can build on these events.

For viewers watching the series for the first time, the finale makes much more sense when the previous five seasons are watched first.

Line of Duty Season 6 Filming and Production

Season 6 was created by Jed Mercurio and produced for the BBC. Like the earlier seasons, it used Northern Ireland as an important filming location.

• 🎬 Jed Mercurio created the series.
• 📺 The BBC broadcast Season 6.
• 🎥 Filming took place largely in Northern Ireland.
• 📍 Belfast was an important production location.
• 🏙️ Many fictional locations were created using real streets.
• 🎭 The cast filmed complex investigation scenes.
• 🕵️ Interview scenes were important.
• 📋 Police offices formed major sets.
• 🚨 Action scenes added tension.
• 🎬 Production balanced drama and investigation.
• 📺 Six episodes were produced.
• ⭐ Kelly Macdonald joined the main cast.
• 👮 Returning actors continued their roles.
• 🧩 The production kept major plot details secret.
• 🎞️ The finale was filmed with careful spoiler control.
• 🌟 The production continued the show’s established style.

Line of Duty Season 6 in 2026

For viewers searching for Line of Duty season 6 in 2026, the season remains particularly relevant because it is the immediate story before the confirmed seventh season.

• 📺 Season 6 originally aired in 2021.
• 🔎 It remains part of the main storyline.
• 👮 Steve returns in Season 7.
• 👮 Kate returns in Season 7.
• 🧑‍✈️ Hastings returns in Season 7.
• 🧩 The Season 6 ending affects the future.
• 👤 Buckells’ “H” reveal is important.
• 🏢 AC-12’s future becomes a major question.
• 🎬 Season 7 moves the story forward.
• 📺 Watching Season 6 helps prepare for Season 7.
• 🔎 The corruption storyline remains important.
• ⭐ The season is still widely discussed.
• 📋 Its ending provides important character context.
• 🕵️ Davidson’s storyline is central to the season.
• 📺 It remains an essential part of a full series rewatch.
• 🌟 2026 viewers can use it as a bridge to Season 7.

Frequently Asked Questions About Line of Duty Season 6

These are some of the most common questions about the sixth season.

• ❓ When did Line of Duty Season 6 air? It aired in 2021.
• 📺 How many episodes are in Season 6? There are six episodes.
• 👩 Who is Joanne Davidson? She is the senior detective investigated by AC-12.
• 🎭 Who plays Joanne Davidson? Kelly Macdonald.
• 👮 Who plays Steve Arnott? Martin Compston.
• 👮 Who plays Kate Fleming? Vicky McClure.
• 🧑‍✈️ Who plays Ted Hastings? Adrian Dunbar.
• 👤 Who is “H” in Season 6? Ian Buckells is revealed as the person behind the “H” mystery.
• 🔎 What is Season 6 about? It focuses on AC-12’s investigation into Davidson and a wider police corruption mystery.
• 🧩 Does Season 6 explain “H”? Yes, it provides the major reveal.
• 🚨 Is AC-12 still together at the end? Its future becomes uncertain.
• 📺 Is Season 6 important before Season 7? Yes, because Season 7 continues with the returning central characters.
• 🕵️ Is Season 6 worth watching? Yes, especially if you want to understand the show’s continuing story.
• ⭐ What is the biggest twist? The revelation involving Buckells and “H.”
• 📅 Why is Season 6 still relevant in 2026? It is the most recent completed season before the confirmed Season 7.
• 🎬 Who created Line of Duty? Jed Mercurio.

Conclusion:

Line of Duty season 6 remains one of the most important seasons in the BBC crime drama. It introduced Joanne Davidson, expanded the police corruption storyline, and finally provided a major answer to the long-running “H” mystery. The season also placed Steve Arnott, Kate Fleming, and Ted Hastings under significant professional pressure.

The six-episode story builds carefully toward its finale, where Ian Buckells is revealed as “H.” While that answers one of the show’s biggest questions, the wider corruption network and the future of AC-12 remain complicated. This is one reason Season 6 is so important when looking at the show’s continuing story.

For viewers in 2026, Season 6 is also the ideal season to revisit before watching Line of Duty season 7, especially because Martin Compston, Vicky McClure, and Adrian Dunbar are returning. Understanding the Season 6 ending makes the next chapter much easier to follow.