ITV's McDonald and Dodds – episode 1 ending explained

Who killed Seth – and why?

Turns out, it was Kasha Perry (Cassie Bradley) who shot Seth Murdoch (Sebastian Knapp) – but her father-in-law Max Crockett (Robert Lindsay) was the real mastermind behind the whole scheme.

And it wasn't Seth who Kasha planned to kill.

As DS Dodds (Jason Watkins) discovered, Seth was actually Max's secret lovechild, born out of a relationship he'd had at university and then obliterated from his own personal history.

Max had abandoned Seth and his mum, and the boy had a pretty wretched life – but now he was trying to get back in touch with his (rich and successful) absentee father.

After an initial rejection where Max made clear his distain, Seth had gone rogue and collected details of the other Crockett kids' wrongdoings, sharing them with his dad to demonstrate that he wasn't the only one with issues. And in response, Max seemed to have extended an olive branch with a dinner invitation.

"You promised Seth Murdoch a fancy meal, but he didn't have the right clothes for a swanky restaurant. So you gave him the back door key to this house," DCI McDonald (Tala Gouveia) explained as she confronted Max. And as an apparently-thoughtful gesture (but actually as part of a dastardly plan), he left out a set of his own clothes and his own hat for Seth to wear.

Max told Seth he'd meet him downstairs, but in reality Max was far away having dinner with his wife and establishing his alibi. So Seth came downstairs in the dark (because Max had made sure the light wasn't working) – and was shot to death by Kasha.

Kasha shot Seth because she thought he was Max. That's exactly what she was meant to think, and that's why poor Seth had been lured to the house and dressed up in his dad's clothes.

Max wanted his inconvenient son out of the picture – forever.

• Meet the cast of McDonald and Dodds

Why did Kasha want to kill Max Crockett?

Kasha is the wife of Max's daughter Elenora Crockett (Ellie Kendrick), and they've established a nice life and a little bakery together. But Max had never accepted Kasha as one of the family, and now he'd come up with a plan to use her as a pawn in his game.

"You'd been working on the killer, stoking up her hatred of you," McDonald told Max. "You knew she had a gun. You knew she despised you with all of her heart and you knew she had a short fuse." Max started goading Kasha, telling her she was scum and not good enough for his daughter.

Then, on the night of the murder, Max told Kasha he'd amended his will to leave his fortune to Elenora. But there was one condition in the will: Kasha would have to leave her wife.

Quite implausibly, Max knew that this revelation would whip Kasha up into such a frenzy that she'd grab her gun (a black market purchase, for protection from an angry ex-boyfriend). She would obviously drive directly to his house and let herself in through the back door, and she would somehow arrive at exactly the right time to shoot Seth (aka fake Max), who would also have arrived at exactly the right time to get ready and would have obeyed his father's instructions to the letter.

Once Kasha realised she'd shot someone else (and not Max), her father-in-law then had blackmail leverage. He didn't tell the police she had a back door key, and he could threaten to grass Kasha up unless she persuaded her wife Ellie to take over the family business – which she did.

• Where is ITV detective drama McDonald and Dodds filmed?

How did McDonald & Dodds work out the truth?

Max Crockett thought he had things all figured out – and he would have gotten away with it too, if it weren't for that meddling Dodds.

We knew from the beginning that Max faked the break-in by kicking in the back door himself, because we saw him do it. But it was actually Mrs Crockett (Natalie Mendoza) who provided the final clue that solved the puzzle.

To explain the fact that the floor was dry even though the bashed-in door was supposedly open all night in the pouring rain, Max secretly turned the underfloor heating on before the police arrived. He could then claim that he'd forgotten to turn the heating off before he left for the weekend.

But no! His "young wife" later mentioned to Dodds that she'd absolutely, definitely switched off the heating before they left the house. So it wasn't on after all.

None of this was watertight evidence, so McDonald provoked an actual confession out of Max Crockett by goading him and insulting him and pretending to have solved the case – by arresting Elenora 'Ellie' Crockett as the shooter.

"No no no, not my daughter," he roared. "I got Kasha to kill him, you stu-"

Success!

Were the other children involved any way?

In this King Lear-style story, two of Max Crockett's daughters were suck-ups greedy for their father's fortune – and one was blameless and content with her lot.

But even though daughters Megan (Rosalie Craig) and Tamara (Susannah Fielding) and their respective spouses had their hidden secrets (corruption, pimping, sex work), they were not responsible for Seth's murder.

However, the secrets uncovered by their unknown half-brother Seth did make their way back to Max Crockett, contributing to his decision to pass on the company solely to (unwilling) Ellie. She was the only one with a clean background.

What happens next?

Kasha and Crockett were both arrested, and poor old Mikey Wallace (Roger Evans) will be free to go after his confession is shown to be false. So that's that for the Crockett family.

But that's not all for McDonald & Dodds! Next time, in episode two, "the chalk-and-cheese detective duo are called to a private clinic where a wealthy patient has been killed. However, their investigation is made all the more difficult by the complex relationships of the victim's former fellow residents."

McDonald & Dodds returns with episode 2 on Sunday 8th March at 8pm on ITV