The Jetty ending explained: who killed Amy Knightly?

The Jetty is a thriller starring Jenna Coleman as a recently widowed detective, Ember Manning, who uncovers dark secrets in the sleepy town she's always called home. But as Ember gets close to the truth, it threatens to destroy her life – forcing her to re-evaluate everything she thought she knew about her late husband, Mack, and the life they built together.

Here is everything that happened in The Jetty episode 4, the final installment of the crime thriller...

The Jetty episode 1
The Jetty episode 2
The Jetty episode 3

The last episode opens with Ember's mum, Sylvia, and Mack in a flashback where she is cleaning a bad cut on his hand. She tells him that Ember isn't happy he is going to miss her 17th birthday and he tells her that he's on a night shift and lies that he cut his hand slicing a bread bap. At the boat house, Amy and Caitlin join Mack and Joe outside and she asks after his hand, revealing that it was her who cut him during their argument and it was his blood that Caitlin saw all over the floor.

In the present day, we see Ember being questioned following her arrest. DI Morgan has the bone fragment that they found in the locker and he confirms that it is Amy Knightly's. Morgan asks her to help them find the rest of Amy's remains because they weren't in the boat hut with the bone fragment, and Ember tells him she can't help becasue she doesn't know anything.

Ember gets home, having been released on bail, and it is the anniversary of Mack's death, so they have a special breakfast to remember him. Ember tries to tell Hannah about the evidence that was found but she doesn't want to hear it. She wants to scatter her dad's ashes at the jetty, but Ember tells her they can't because of the police investigation.

In a flashback Amy is telling Caitlin that she is planning to sleep with Mack for the first time and encourages Caitlin to sleep with Joe at the same time so they both lose their virginity at the same time. It is clear that Caitlin doesn't want to, but agrees to to make Amy happy. The girls kiss and Joan, Caitlin's mum, sees them but hides it from Caitlin's dad.

In the present day, Ember, Sylvia and Arj and Hannah all have a toast to Mack on the anniversary of his death, but when Hannah asks her mum to say some words about Mack, Ember struggles to know what to say. Hannah gets cross and wants to know what is wrong, and Ember admits they found Amy's bone at the boathouse and Hannah races out of the house, throwing Mack's ashes on the floor outside in a rage. Ember is left to try and scoop them back into the urn while Hannah tells her mum she needs to prove Mack's innocence.

Ember goes to see Joan at the care home again to ask who Kitty is, but the doctors have given her a sedative after she became agitated following Ember's last visit. Caitlin's father tells Ember that Kitty is a nickname for Caitlin and asks her to leave.

Who is Joe?

Ember manages to track a now grown-up Caitlin down at a university where she works as a lecturer. At first, Caitlin pretends to Ember that she doesn't know who Amy Knightly is, but when Ember shows her the photo she found in Mack's study, Caitlin softens. She tells Ember that Amy is probably out there living a full life after running away 17 years ago, but when Ember breaks the news Amy is dead, Caitlin is devastated.

Ember asks her why she lied to the police about being with Amy the night she went missing, but Caitlin says her mum warned her to keep a distance because if the police found out she was in love with Amy, then they might link her to the crime. Ember asks Caitlin who took the photo and she says it was Joe, Mack's brother, which leaves Ember speechless because she didn't know her late husband even had a brother.

She tells Hitch about Joe, but Hitch is more worried about losing his job if anyone sees him spending time with her now that she is suspended. Ember asks for his help with going to see Joe, who is in prison. Hitch doesn't understand how he could have killed Riz, but Ember reveals that Joe has been going out on day release, including the day Riz was killed.

They go to see Joe in jail and he tells them he hasn't seen Mack in years and lies that he doesn't know who the girl in the photo of Amy and Mack is. A flashback reveals that he does know because he took the picture on the night Amy went missing. But while Ember seems convinced that he is the one who killed Amy, Joe is clearly shocked when she tells him Amy is dead and her remains were found at the boat hut meaning he isn't guilty.

In the flashback we see Joe and Caitlin sleeping together at the same time as Amy and Mack, just like the pact they had made. But when Joe reveals that it isn't the first time his brother has slept with Amy, Caitlin realises her best friend lied to get her to sleep with Joe so she races off, upset.

Amy follows and the girls argue when Caitlin works out that they are friends because Joe has been blackmailing his brother and threatening to report him to the police for sleeping with a minor if they didn't find him someone to sleep with too. Caitlin is heartbroken to realise that she has been used, but as they argue they end up kissing. Caitlin breaks things off though, telling Amy that she loves her before walking away.

Back at the boathouse, Mack breaks up with Amy, telling her that he is going, he doesn't love her and feels bad for what they did to Caitlin. He tells her to go after Caitlin because she is in love with her. Amy begs him not to leave and breaks down... but as they are fighting Joe steals Mack's car keys and runs out.

Who killed Riz Samuels?

In the present day, Ember is in her old bedroom at her mum's and she remembers the night of her birthday and Mack is singing a song he has written to her. He tells her he has to go to work (which we now know is actually meeting Amy and Caitlin that last time because Joe is blackmailing him) and he says he is sorry to miss her party at the pub. He gives her some drugs but Ember remembers that they made her sick.

She talks to her mum, asking again about the night that Amy went missing and Sylvia tells Ember that she left her own party early and when Sylvia got home later Ember and Mack were already there. Ember asks about the drugs, but Sylvia doesn't think it is a big deal, and reveals that Mack didn't stay over that night because they had a job to do.

Ember questions who 'they' are and soon the penny drops and she heads to the boathouse where she finds Arj. He is drinking alone at the jetty and she tells him she knows he was with Mack the night Amy went missing. But he is drunk and asks her if they could have ever been a couple, a comment that Ember ignores - however as they are talking the noise from a boat in the dock reminds Ember of something and she releases it is the same noise she heard in the background of the sound file of Riz being murdered.

Realising that Arj killed Riz, Ember tries to run, but Arj stops her and tells her what happened, claiming that he didn't set out to hurt her, but she came looking for him. He explains that the bone fragment was in the boat hut because of him, he heard the floor was being pulled up by the builders and so he broke in, dug up the body, and then set fire to the boathouse to cover his tracks.

Who killed Amy Knightly

Ember tells Arj he should have let Amy's body be found and let Mack get the blame for what he did, and let Riz live. However, Arj drops the bombshell that he didn't just kill Riz, but he also killed Amy too - it wasn't Mack.

Ember's stunned as he tries to get her to listen, telling Ember that the night of her birthday they were at the pub and he felt sorry for her becasue Mack wasn't there and he knew where he really was - that he was with Amy - and that she deserved better. He reminds Ember that she was giving out pills and everyone was having a good time, but then he realised Mack had been leaving him messages and asking him to pick him up from the boathouse.

In flashbacks we see someone driving down a dark road and picking up Mack, but as they drive off they hit Amy, who is standing on the side of the road. Mack tells the driver it was just a log, but he is lying. In the present, Arj is explaining that he doesn't remember driving the car and that the first thing he remembers is being asleep in bed when Mack wakes him and tells him he hit Amy in the car and they have to get rid of the body. He says she had fallen down an embankment and had hit her head on a rock. They were going to put her in the lake, but Mack said the basement of the boat house was kinder.

But as Arj is talking about that night, Ember finally pieces together all her flashbacks and realises that Arj wasn't driving the car that night, she was. She killed Amy, and Mack covered for her to protect her.

Arj tells Ember that Amy's death has ruined his life, and they get into an argument when Ember tells him they have to go to the police and tell them the truth. But knowing he will go to jail because he killed Riz, Arj flips and strangles Ember, trying to kill her in the same way he killed Riz.

Does Ember Manning go to jail?

Ember comes to and is now at the end of the jetty and Arj is throwing petrol all over her, the jetty and himself. Ember begs for her life, but Arj tells her that he did it all for her and that people do odd things for love. She tells him that isn't love, but as she is talking he sets fire to himself and the jetty... and she has to jump into the water to save herself from going up in flames.

Ember is later at a police station having photos of her bruised neck taken, and the next day she is sitting in the car with Caitlin who is cross with her for not telling her last time they met that Malachy was her husband. Ember apologises and Caitlin tells her that Amy wasn't safe from any man, but Ember corrects her and confesses that she was the one driving the car and not Arj. Ember reveals how she didn't know she was the one who killed Amy and tells Caitlin that she is going to hand herself in. Caitlin questions if the truth and justice are the same thing, suggesting she doesn't think Ember should hand herself in after all this time.

At the police station, Ember is being questioned and as DI Morgan asks her to tell them everything she knows, she says she was there the night that David 'Arj' Argent killed Amy Knightly... pinning the blame on Arj instead of confessing what really happened.

We then see grown-up Caitlin visiting her mum at the care home and her parents are thrilled. Meanwhile, Ember is with Miranda and her baby in the hospital she tells Miranda that she is going to need a list of all the men she had underage sex with so that she can put them, and Liam, in prison. She tells Miranda she needs to make the world a safer place for her daughter by putting the men in jail.

The episode ends with Ember, Hannah and Sylvia at the lake where they scatter Mack's ashes at last. Ember says that Mack did things he shouldn't have, but that doesn't mean they will stop loving him. Sylvia apologises to Ember for not being the best mother and tells her that she hopes it isn't too late to make amends before they all hug.

All episodes of The Jetty are available to watch on BBC iPlayer now.

Episodes will air on BBC One on Monday, July 15, Tuesday, July 16, Sunday, July 21, and Monday, July 22 all at 9 pm.