Warning: Major spoilers ahead

With Josie holding the entire Irvine family at gunpoint, she is insistent that Milo is actually her son. Milo stirs on the baby monitor, and she insists she wouldn’t hurt him, but the distraction is enough for Colin to jump in and try and get the gun off her.

It goes off, and Colin is badly wounded in the stomach, sending everyone into a frenzy. Josie insists she didn’t want to hurt anyone but refuses to put the gun down despite pleas from everyone around her. She allows someone to call an ambulance, with Lia being allowed to leave to let them in, while Peter puts pressure on Colin’s wounds to try and keep him alive.

As Milo starts calling out for his mommy, Peter asks if Marissa can go to him, so he doesn’t come downstairs to see what’s going on. Josie agrees she doesn’t want Milo to see any of it, but refuses to let Marissa leave, telling Brian to go instead. Marissa begs him to protect Milo.

By the time they do this, Colin has bled out on the floor and died.

While Josie insists she didn’t want to hurt anyone, Marissa demands to know who she is, and why she took Milo. She introduces herself by her real name – and Marissa immediately recognises it, saying she thought she had died. Josie said she wanted to, but was very much alive.

She insists she wasn’t here to get him back, as she knows she can’t have him, but says that “they won” and to promise, mother-to-mother, that she’ll protect Milo from Peter.

Confused, Marissa asks what she means, Josie says that Peter did something that night before the ambulances came. While she knows she won’t believe her, she needs to hear it for herself, pulling out a phone from her back pocket.

Peter lunges at Josie, turning the gun on her and shooting her dead to Marissa’s horror. He then instructs Marissa to go outside and wait with Lia. Marissa tells him that he didn’t have to shoot her. He insists that he didn’t and “it just went off” but she knows what she saw and demands to know what was so bad that he couldn’t have Josie reveal it.

She then asks the dreaded question: “Whose baby died in that accident?” and when he refuses to answer, she threatens to tell the police what actually happened. He tries to call her bluff, saying as he’s her husband, she wouldn’t, but she says to try her.

On October 1st, six years ago, the Irvines were the other car involved in the crash with Josie and her baby, Noah. Peter was protected by the airbag, but in the backseat Milo died, and he thought Marissa, who was in the backseat with the baby, had died too, with her head having been smashed through the window.

In shock and grieving, he called for an ambulance but then heard another baby crying in the other car. Thinking Josie was dead, he picked the crying baby up to soothe him after the crash. With the tot miraculously unharmed, and with the ambulance sirens drawing closer, he made the decision to switch the babies out. He justifies it by saying it felt like the baby was supposed to be theirs.

Horrified, Marissa tells him the baby wasn’t theirs – it was Josie’s, and he stole a child. He continues to fight it, saying she was in no position to raise a baby, or give him the life that they could, so he did what he thought was right. He argues that his decision saved all of them, which mortifies Marissa even more.

Marissa realises that the past six days of torment over Milo’s kidnap were never her fault like he wanted her to think. It was his. As sirens and emergency services pull up outside, she asks what was on the phone, and Peter says he doesn’t know and it doesn’t matter – but she needs to cover for him over Josie’s death because if authorities know the truth, they’ll try to take Milo.

Detectives Alcaras and Greco arrive on the scene, and question if they knew the Murphys. Peter gives a glossed over version of what happened, mentioning the crash but not the baby switch, sticking to the story that Milo survived and Josie’s baby didn’t.

He also claims that he had shot Josie while grappling with her for the gun, under the impression she was going to kill everyone there. Marissa stays silent but knows that’s not true – she had offered for him to take it and had repeatedly said she didn’t want to hurt anyone.

Alcaras is spotting holes in the story too, wondering why Josie would let Lia call an ambulance for Colin, or let Brian take care of Milo, if murdering everyone was her true intention. Asking if there was anything more going on, Peter insists Josie must have just been mentally unwell. Alcaras asks Marissa, but she decides to follow Peter’s story.

However, later that night, she takes the phone Josie had and finally listens to the audio recording she had tried to show her. The recording captured Peter arriving to drop off a ransom to Josie’s father, Rob. Rob comments that it would be “the kind of story the press would love” as Peter hands the money over, before Peter kills Rob with a lamp, taunting the body that he was “his son”.

Running back into the house, Peter notices something wrong and chases after her, asking what’s wrong. Marissa tells him, and he reacts calmly, telling her that he “got Milo back for her” while he went to get upholstery cleaner for her. He was also the one that put Milo in the trunk of the car to be found safely and made sure he didn't see what he’d done. Peter insists they would never have been safe while Rob was alive because he would have kept demanding more from them.

Marissa is shaken, edging her way up the stairs as Peter follows her, telling her to hand the phone over to him so he can get rid of it. He tells her that Milo would be taken from them if the truth ever got out, and he would take care of everything. When she does, he tells her he loves her, and she needs to understand he did what he did to protect their son.

He leaves her keeled over on the stairs, feeling sick.

The next day, Alcaras and Greco debrief on the bizarre case, with ballistics confirming Josie was holding the gun when it was fired, and with her breaking into the Irvines’ home, it seems pretty open and shut. Alcaras notes he can never prove Peter deliberately shot her, suggesting he thinks he did, and admits he feels like “they’re missing something”, still unsure why Josie went to the house that night.

As Peter plays with Milo, a heartbroken Lia arrives at the Irvines’ house, with Marissa comforting her, confirming that Colin didn’t survive the shooting. Lia is now busy organising the wake, but she’s struggling, joking it’s “adult stuff”. Marissa reassures her that she’s doing fine.

That night, Marissa lies in bed with Milo, who appears completely unphased and unaware of everything that’s happened around him the past few days. Peter joins them, whispering that the police have closed the investigation. He smiles as he tells her “It’s over” and things can “go back to how they were”.

The next morning, Milo asks when he can go back to school because he’s bored, but Marissa admits to Peter she’s still too scared to let him out of her sight. Milo proudly shows his dad he’s learned how to hold his play scissors, but he tells him off, saying that “you need daddy for the scissors” and takes them off him, even though Milo insists he can do it himself.

Milo runs off in a strop and Peter grabs him and holds him roughly, telling him he’s not allowed to run away from him because “you’re mine”. Marissa witnesses it and becomes terrified about the control Peter has over Milo, remembering how often Peter has said that about him to justify killing both Josie and Rob.

Jenny has hired Esther as her new nanny and is far more present at work as a result. Marissa asks to see her and later goes over to her house to tell her everything.

Marissa knows she’s in a bind because if she goes to the police, it’ll confirm Milo’s not their son, and he could be taken away; she can’t stay with Peter, who has become too controlling to bear; but if she leaves, she doesn’t know what he’s capable of. So what can she do?

Outside of work, Alcaras takes Sam for a medical examination ahead of his start at St Mark’s School. As part of the consultation, he’s asked if Sam sees shapes when hearing sounds, and the doctor tells him that, while it's a rare phenomenon, some people who are neurodivergent have a crossover of senses, meaning they taste colours or objects when saying their names, or associate colours with things like days of the week. Alcaras realises that Milo exhibits those traits.

As Marissa loosens up her protectiveness, she allows Milo to go on a playdate with Joshua, Jenny’s son, while she attends Colin’s funeral. As they get ready, she tells Peter that she’s ready to move on from it all, which he sees as a positive sign.

Meanwhile, Alcaras looks into Josie’s past, calling up her guidance counsellor from school who said she got “overwhelmed” when words, tastes and colours got mixed up in her head, though her parents never took her to a doctor. He notes it’s a condition called synesthesia – and it's a trait usually inherited by parents.

At the funeral, Peter gives Brian the side-eye for using his wheelchair. When Brian calls him on it, saying he’s happy to be in his wheelchair, Peter asks if it’s his way of getting back at him. Brian tells him it’s got nothing to do with him and he actually forgives him for what he did – but also doesn’t want Peter to take care of him anymore.

With the chair, he’s able to stop taking the pain medication that makes him so drowsy, he’s found an assisted living facility to move into and will be looking for a new job so he can live life on his own terms. Peter secretly rages, but Brian is clearly more confident than ever.

Peter then goes to check on Lia, saying she did a good job with the wake. She tells him that Colin’s house has been sold, which will cover his debts to the firm. He comforts her, saying he was a good guy, but can’t resist making a dig, saying he wasn’t sure if the two of them as a couple was “the right call”.

When she says that she loved him, he tells her that their relationship triggered the entire spiral, and “she needs to remember that”.

Marissa later finds Peter in the wine cellar, and he asks how she’s holding up. She says she’s doing OK, and then passionately kisses him, telling him she missed him. Seconds later, he starts to come over slightly funny, struggling to breathe.

Realising she hadn’t checked all the food allergens properly at the buffet, she tells him she might have had soy by accident – something he’s deathly allergic to. He heads upstairs to get his epipen from his jacket, jabbing himself in the leg but it’s expired. She then calls Lia, telling her to call 911 and get an emergency kit from their car.

Lia runs back to say the emergency kit wasn’t in the car, and the ambulance was eight minutes away. Knowing that he doesn't have that long, Peter tells Marissa “You always have an emergency kit” and she switches, agreeing with him. He realises she did it deliberately.

As this unfolds, Alcaras visits the paramedic who attended to the crash six years ago to ask questions. The paramedic confirms the only people awake at the scene was Jake and the baby, with everyone else unconscious. As he leaves the hospital, he gets a call that Peter Irvine is dead.

Alcaras and Greco recount the case, looking back at the eight suspects on the wall and reflecting on everything that’s happening. Greco is convinced that Peter dying was no accident, and there’s more to the story, believing Marissa orchestrated his death after something Josie said the night she died.

Despite his own investigation, Alcaras decides to keep quiet, saying that they’ll “probably never know”. But they have one more person to investigate: Lia. And she’s lawyered up.

In the interrogation room, they question Lia about Marissa, and how meticulous she is when it comes to checking food labels. While we know Marissa saw her check the labels, Lia covers for her - saying while she’s not forgetful, she’s human. The last few weeks have been messy for the family and things happen.

Lia says it’s easier to blame and accuse people because it’s a comfort to have someone punished for what happened, but she’s not going to put Marissa at fault for the death of her brother. Greco pushes, asking if she is to blame, wouldn’t she want to know? In response, Lia says she didn’t see Marissa read the food labels – while remembering Peter’s bitter comments towards her at the wake.

Alcaras takes Sam for his first day at St Mark’s, and he thrives immediately, excited with the games and the dog waiting outside. Despite knowing he bent rules to get him there, Alcaras knows that he ultimately did the right thing for his son.

He later goes to visit Marissa, who is packing up the house in order to move, and shares with her his thoughts about Milo having synesthesia. He notes it’s normally inherited, and Josie had it too. She looks at him terrified as he heavily infers that he knows the truth about Milo being switched in the crash but knows she wasn’t part of it. He’s also guessed that Peter was behind Rob Murphy’s murder.

However, he adds that he knows she didn’t know about any of it until the night Josie turned up at her house, and was forced to “make some choices” to protect her son. He assures her the case is closed, and tells her that, while he thought he would care more about bending the law this way, he’s actually OK with it. Before she can respond or say anything, he leaves.

Now free to take care of Milo by herself, Marissa takes him to see Jacob at Jenny’s house. Together, the women watch the boys play over a glass of wine, feeling relaxed and happy.