Line of Duty Season 4 is one of the most popular seasons of the British police thriller Line of Duty. First broadcast in 2017, the season follows Detective Sergeant Roz Huntley as she becomes the focus of an investigation by AC-12, the anti-corruption unit. The story mixes police investigations, hidden motives, tense interviews, and difficult questions about trust and evidence.
Season 4 stars Thandiwe Newton as Roz Huntley, with Martin Compston, Vicky McClure and Adrian Dunbar returning as Steve Arnott, Kate Fleming and Ted Hastings. With its famous interview scenes and unexpected twists, the fourth season remains an important part of the show’s story.
What Is Line of Duty Season 4 About?
Season 4 centers on Roz Huntley, a senior detective investigating a difficult murder case. Her work attracts the attention of AC-12 after questions arise about the way the investigation is being handled.
- 👮 Roz Huntley leads the case
- 🕵️ AC-12 investigates police conduct
- 🎭 Thandiwe Newton plays Roz
- 👮 Steve Arnott returns
- 👩 Kate Fleming returns
- 👨 Ted Hastings returns
- 🔎 Evidence becomes important
- 🧩 The case has hidden secrets
- 🚨 Police corruption is examined
- ⚖️ Investigators question official decisions
- 📝 Interviews reveal new information
- 👀 Characters are not always what they seem
- 🔄 Suspicions change throughout the season
- 😲 Major twists affect the case
- 🧠 Viewers must follow small clues
- ⭐ The season builds toward a major reveal
The season is designed around uncertainty. Viewers are encouraged to question Roz’s decisions while AC-12 tries to understand what really happened.
Line of Duty Season 4 Cast
The Line of Duty Season 4 cast includes several returning stars alongside Thandiwe Newton, who plays the season’s central character.
- 🎭 Thandiwe Newton — Roz Huntley
- 👮 Martin Compston — Steve Arnott
- 👩 Vicky McClure — Kate Fleming
- 👨 Adrian Dunbar — Ted Hastings
- 👮 Craig Parkinson — Matthew “Dot” Cottan
- 🎭 Lee Ingleby — Nick Huntley
- 👩 Royce Pierreson — Jamie Desford
- 👮 Jason Watkins — Tim Ifield
- 👩 Claudia Jessie — Jodie Taylor
- 🎬 Patrick FitzSymons — Jimmy Lakewell
- 👮 Maya Sondhi — Maneet Bindra
- 🕵️ AC-12 members return
- 🎭 Supporting police characters
- 🔎 Investigators expand the story
- ⭐ Strong ensemble cast
- 📺 BBC crime drama
Thandiwe Newton’s performance gives the season a different feel because Roz is both an experienced detective and the subject of AC-12’s investigation.
Thandiwe Newton as Roz Huntley
Roz Huntley is the main character of Season 4. She is a Detective Chief Inspector leading a major investigation. Her professional confidence is tested when AC-12 begins asking questions about her methods.
- 👮 Senior police detective
- 🎭 Played by Thandiwe Newton
- 🔎 Leads a major investigation
- 🧠 Experienced investigator
- 💼 Strong professional reputation
- 🏠 Has a family life
- ⚖️ Faces serious accusations
- 🕵️ Investigated by AC-12
- 📝 Her evidence is questioned
- 👀 Her actions attract suspicion
- 🔄 Her story changes over time
- 🧩 Connected to several mysteries
- 🚨 Under professional pressure
- 🎯 Tries to protect her case
- 😲 Becomes central to the season
- ⭐ One of the show’s memorable characters
Roz is an interesting Line of Duty character because the audience sees events from both sides: her own investigation and AC-12’s attempt to investigate her.
Steve Arnott in Season 4
Steve Arnott remains an important member of AC-12 during Season 4. He works with his colleagues to investigate the questions surrounding Roz Huntley’s case.
- 👮 Steve Arnott
- 🎭 Played by Martin Compston
- 🕵️ AC-12 investigator
- 🔎 Investigates police misconduct
- 📝 Examines evidence
- 👀 Questions witnesses
- ⚖️ Looks for inconsistencies
- 🤝 Works with Kate and Hastings
- 🧠 Uses investigative reasoning
- 🚨 Faces dangerous situations
- 🎯 Follows evidence
- 🧩 Connects clues
- 🏢 Works within AC-12
- 📺 Central returning character
- ⭐ Experienced investigator
- 🔄 His story continues beyond Season 4
Steve’s role helps connect the fourth season to the wider AC-12 story. His investigation also gives viewers another perspective on Roz and the police case.
Kate Fleming in Season 4
Kate Fleming is another important AC-12 investigator. She brings a different approach to the investigation and works closely with Steve and Hastings.
- 👩 Kate Fleming
- 🎭 Played by Vicky McClure
- 🕵️ AC-12 investigator
- 🔎 Examines police cases
- 📝 Studies evidence
- 👀 Observes details
- 🧠 Analytical approach
- 🤝 Works with colleagues
- 🚨 Investigates suspicious behavior
- ⚖️ Focuses on police integrity
- 🧩 Follows important clues
- 🏢 Works within AC-12
- 🔄 Her career continues
- 🎯 Helps develop the investigation
- ⭐ Major returning character
- 📺 Important part of the season
Kate’s investigative style adds balance to the AC-12 team. Her experience as a police officer also helps her understand how investigations work from inside the force.
Ted Hastings in Season 4
Ted Hastings is the head of AC-12 and continues to lead the team’s fight against police corruption.
- 👨 Ted Hastings
- 🎭 Played by Adrian Dunbar
- 🕵️ AC-12 leader
- 👮 Senior police officer
- 🔎 Oversees investigations
- 📝 Reviews evidence
- ⚖️ Focuses on police integrity
- 🧠 Experienced leader
- 🤝 Supports his team
- 🚨 Takes corruption seriously
- 🎯 Wants clear answers
- 🏢 Leads AC-12
- 📺 Long-running character
- ⭐ Strong leadership role
- 🔄 Faces new challenges
- 🧩 Connects Season 4 to the wider story
Hastings remains one of the central figures in Line of Duty. His leadership gives AC-12 its direction while the team deals with a complicated and increasingly dangerous case.
Line of Duty Season 4 Episodes
Line of Duty Season 4 has six episodes. Each episode continues the investigation while gradually revealing more information about Roz Huntley and the case.
- 📺 Six episodes
- 🎬 Episode 1 begins the new case
- 🔎 AC-12 starts asking questions
- 👮 Roz Huntley becomes central
- 🧩 New clues appear
- 📝 Evidence is examined
- 👀 Witnesses are questioned
- 🚨 Suspicion grows
- 🔄 The investigation changes direction
- 😲 Major revelations appear
- 🧠 Viewers must follow clues
- ⚖️ Police decisions are challenged
- 🕵️ AC-12 continues investigating
- 🎯 The pressure increases
- 🏁 The story reaches a major conclusion
- ⭐ Strong season-long mystery
The six-episode format keeps the story focused. Each episode adds another layer to the investigation rather than resolving the mystery immediately.
Line of Duty Season 4 Episode 1
The opening episode introduces Roz Huntley and the investigation that eventually brings her into AC-12’s focus.
- 👮 Roz leads an investigation
- 🔎 A serious case is introduced
- 🧩 Important evidence appears
- 📝 Police procedures become important
- 🕵️ AC-12 begins watching events
- 👀 Roz faces questions
- 🎭 New characters are introduced
- 🏠 Family life is shown
- 🚨 Professional pressure grows
- ⚖️ Evidence becomes disputed
- 🔄 The investigation develops
- 🧠 Viewers receive early clues
- 🎯 AC-12 begins building its case
- 😲 Suspicion starts growing
- 📺 The season’s mystery begins
- ⭐ Sets up the remaining episodes
The first episode establishes the central conflict between Roz’s investigation and AC-12’s concerns about how that investigation is being conducted.
Line of Duty Season 4 Episode 2
Episode 2 increases the pressure on Roz as AC-12 continues to investigate. The story begins connecting different pieces of evidence.
- 🔎 AC-12 investigates further
- 👮 Roz continues her work
- 📝 Evidence is reviewed
- 🧩 New information appears
- 👀 Characters become suspicious
- 🚨 Pressure increases
- 🕵️ Interviews reveal details
- ⚖️ Police procedures are questioned
- 🔄 The case develops
- 🧠 Small clues become important
- 🎭 Relationships are tested
- 📺 The investigation expands
- 🎯 AC-12 searches for answers
- 😲 New questions appear
- 🏠 Roz’s personal life matters
- ⭐ The mystery deepens
The second episode helps establish the season’s main pattern: information is revealed gradually, while the characters try to decide which evidence can be trusted.
Line of Duty Season 4 Episode 3
By Episode 3, the investigation becomes more serious. AC-12 has more reasons to examine Roz’s actions, while the case itself continues to develop.
- 🕵️ AC-12 increases its investigation
- 👮 Roz faces more pressure
- 🔎 Evidence becomes central
- 📝 Statements are examined
- 🧩 Clues connect
- 👀 Suspicion increases
- ⚖️ Professional decisions are questioned
- 🚨 The stakes rise
- 🧠 Investigators study details
- 🎭 Relationships become tense
- 🔄 The story takes new turns
- 🏢 Police politics become important
- 🎯 AC-12 wants answers
- 😲 New revelations appear
- 📺 The mystery becomes deeper
- ⭐ The season reaches its midpoint
The middle of the season is where the investigation becomes increasingly complicated. Viewers have to reconsider earlier assumptions as new information changes the picture.
Line of Duty Season 4 Episode 4
Episode 4 continues the pressure on Roz and AC-12. The investigation becomes increasingly difficult as the characters attempt to establish what happened and who can be trusted.
- 🔎 More evidence is examined
- 🕵️ AC-12 follows new leads
- 👮 Roz remains under pressure
- 📝 Interviews become important
- 🧩 Clues are connected
- 👀 Suspicion spreads
- 🚨 Danger increases
- ⚖️ Police integrity remains central
- 🧠 Investigators challenge statements
- 🎭 Relationships become complicated
- 🔄 New information changes theories
- 🏢 Internal police issues appear
- 🎯 AC-12 seeks proof
- 😲 Major questions remain
- 📺 The mystery continues
- ⭐ Tension builds toward the finale
The fourth episode pushes the season toward its final stage. The difference between evidence, assumptions and personal claims becomes increasingly important.
Line of Duty Season 4 Episode 5
Episode 5 prepares the story for its conclusion. Important information begins coming together while the investigation becomes more urgent.
- 🕵️ AC-12 moves closer to answers
- 🔎 Evidence is connected
- 👮 Roz faces major pressure
- 📝 Statements are challenged
- 🧩 Earlier clues become important
- 👀 Suspicion reaches a high point
- 🚨 The case becomes urgent
- ⚖️ Police decisions are examined
- 🧠 Investigators reassess theories
- 🎭 Characters reveal more
- 🔄 The investigation changes direction
- 🎯 AC-12 needs evidence
- 😲 New revelations appear
- 🏢 Police relationships are tested
- 📺 The finale approaches
- ⭐ Tension reaches a peak
This episode is important because several earlier details start to make more sense. It creates the foundation for the final episode’s major revelations.
Line of Duty Season 4 Episode 6
The sixth episode brings the main investigation to a conclusion. It answers major questions while also leaving the wider Line of Duty story open for future seasons.
- 🏁 Season 4 reaches its finale
- 🔎 Major evidence is revealed
- 🕵️ AC-12 completes key work
- 👮 Roz’s story reaches a turning point
- 🧩 Important clues connect
- 📝 Evidence is reassessed
- ⚖️ Police accountability remains central
- 🚨 The investigation reaches its peak
- 👀 Characters face consequences
- 🧠 Earlier events become clearer
- 🎭 Major performances drive the episode
- 🔄 The wider story continues
- 📺 The season closes
- ⭐ Important AC-12 developments remain
- 🏁 The central case reaches an outcome
- 🔎 Future questions remain
The finale provides the answers viewers have been waiting for while keeping the larger world of Line of Duty open. That balance became an important feature of the series.
Line of Duty Season 4 Ending Explained
The Season 4 ending resolves the central mystery surrounding Roz Huntley and her investigation, while also delivering an important development involving AC-12 and the wider corruption storyline.
- 🧩 The central mystery is resolved
- 🔎 Important evidence explains earlier events
- 👮 Roz’s actions are examined
- 🕵️ AC-12 gets crucial information
- ⚖️ Accountability becomes important
- 📝 Earlier statements gain new meaning
- 👀 Hidden connections are exposed
- 🚨 The investigation has consequences
- 🧠 The finale rewards careful viewing
- 🔄 The wider story continues
- 🎭 Characters face difficult choices
- 🏢 Police corruption remains a theme
- 🎯 AC-12 continues its mission
- ⭐ The season changes the wider story
- 📺 The ending leads into later seasons
- 🧩 Some questions remain open
The ending is best understood as part of the larger Line of Duty story rather than as a completely separate mystery. Several developments introduced in Season 4 become important later in the series.
Why Line of Duty Season 4 Is Popular
Season 4 remains popular because it combines a strong central performance with the show’s familiar police-investigation style. The tension comes from watching investigators challenge evidence and question whether official accounts can be trusted.
- 🕵️ Strong police investigation
- 🎭 Thandiwe Newton’s performance
- 🧩 Complicated mystery
- 📝 Detailed evidence
- 👀 Unexpected clues
- 🚨 High tension
- ⚖️ Police corruption themes
- 🧠 Smart storytelling
- 🎯 Strong character development
- 📺 Six focused episodes
- 😲 Major twists
- 🏢 AC-12 investigation
- 🎭 Strong supporting cast
- 🔄 Connections to later seasons
- ⭐ Memorable interview scenes
- 🏆 Popular British crime drama
The season also works well for viewers who enjoy detective stories where the answer is not immediately obvious. Its combination of character drama and investigative suspense keeps the story moving.
Line of Duty Season 4 Compared With Other Seasons
Season 4 has its own identity because Roz Huntley becomes both a major investigator and the subject of an AC-12 investigation. This differs from some other seasons, where the central mystery focuses on different types of police corruption.
- 🕵️ Season 4 centers on Roz Huntley
- 🎭 Thandiwe Newton leads the season
- 🔎 AC-12 investigates a serving officer
- 🧩 The mystery develops slowly
- 📝 Evidence is very important
- 👀 Trust remains a major theme
- 🚨 Police corruption continues
- 🎯 AC-12 remains central
- 👮 Steve returns
- 👩 Kate returns
- 👨 Hastings returns
- 📺 Six episodes
- 😲 Several major twists
- 🏢 Police politics matter
- 🧠 Investigation drives the story
- ⭐ Connects strongly to later seasons
For fans of the wider series, Season 4 is especially important because it continues developing the long-running AC-12 storyline while introducing a new central character.
Line of Duty Season 4: What Makes It Worth Watching?
Season 4 is a strong choice for viewers who enjoy British crime dramas, police mysteries and stories built around investigation and suspicion. It offers a focused case while continuing the larger AC-12 narrative.
- 🕵️ Interesting detective story
- 🎭 Strong lead performance
- 🧩 Difficult mystery
- 🔎 Evidence-based investigation
- 🚨 Suspenseful scenes
- 🧠 Smart questioning
- 👀 Hidden details
- ⚖️ Moral questions
- 👮 Police workplace drama
- 📺 Short six-episode story
- 😲 Unexpected turns
- 🏢 AC-12 storyline
- 🎯 Strong character conflict
- 🔄 Links to later seasons
- ⭐ Memorable moments
- 🎬 High-quality British television
If you enjoy stories where every statement may have another meaning, Season 4 offers plenty to analyze. It is also a useful season for understanding the continuing AC-12 storyline.
Conclusion:
Line of Duty Season 4 is a six-episode British police thriller centered on Detective Chief Inspector Roz Huntley and the investigation into her conduct by AC-12. Thandiwe Newton leads the season, while Martin Compston, Vicky McClure and Adrian Dunbar return as key AC-12 characters.
The season is known for its tense investigations, detailed evidence, complicated characters and major twists. It also plays an important role in the wider Line of Duty story, making it a worthwhile season for both new viewers and long-time fans.
David Parker is a content writer focused on motivational lines, personal development messages, and powerful words that inspire action.