A serial killer, an obsessed cop and an undercover FBI agent. Welcome to Apple's 'Nocturne'

To play a serial killer in the new Apple TV series “Nocturne,” Stephen Graham did what all good actors do: He watched a bunch of serial killers.The Emmy- and Golden Globe-winning actor binged on true crime documentaries, handpicked by his wife, Hannah, who he says is slightly obsessed with the genre.“She just kept going, ‘Right, this one’s really good. Watch this one.’ And I was like, ‘All right,’” says Graham. “I watched how they kind of manipulated certain people and how they believed their own truth.”Viewers who tune in starting Friday will find a new frightening side of the “Adolescence” star, who this time plays an imprisoned murderer with ferocious intensity, beguiling hospital staff and frustrating law enforcement as he plots horrible things. All that TV binging of killers paid off, so to speak. “You absorb them,” says Graham. “It’s like kind of going to an art gallery and being inspired by wonderful art. At some point, you may not even be aware of it, but it’ll be something tha