Innocent fans were left proud of themselves tonight after they correctly guessed the identity of Matty's killer.
The series has followed teacher Sally Wright's quest for justice, after she was wrongfully convicted of schoolboy Matty's murder.
Viewers have suggested several people were behind the crime after watching the four-part drama every night this week.
In the final episode Karen was in the frame for Matty's murder after she admitted she had fought with him on the day of his death.
But her daughter Beth told police that she was Matty's real murderer, following his bullying campaign against her.
However police weren't convinced by her tale and their attention turned to Sally's husband Sam after they discovered his alibi was fake.
Sally also uncovered evidence that pointed the blame at Sam.
She found a note that said: "You said you loved me but you wont speak to me, if you don't come I'll tell Sally, I mean it Sam."
Sally confronted Sam and said: "It was you wasn't it."
Sam said: "I would never have hurt Matty but I have lied about who I am and for that I'm so ashamed, I wanted to be a good husband to you."
Sam admitted he had been with Matty and that there had been other affairs before him.
Sam said: "I never meant to hurt him, I told him I couldn't keep seeing him, but he wouldn't accept it, he said I was hurting him, you and myself, it was all so simple for him.
"He was drunk and past caring, he accused me of abusing him and screamed at me he was going to tell everyone who and what I was.
"I don't remember picking up the bottle or going after him, I don't remember hitting him with it, I just remember the surprise on his face afterwards, I just wanted to stop him Sal."
Sally couldn't believe his actions and broke down in tears saying she didn't know how he could put her through that.
He said he was a coward and was taken away and arrested by police.
And viewers were quick to comment on social media, with many of them saying they had predicted Sam was the killer.
Sharon said: "I had a feeling it was Sam, when Anna said she saw Matty going to Sally's house. Knew it was Sam he was going to see not Sally."
Molly said: "Yes I thought so Sam!"
Dr David Honeywell said: "My money was on Sam."
And @bufferb said: "I was right it was Sam who did it, but I didn't guess he liked men."
*Innocent is available to catch-up on the ITV Hub
