Tonight's all new episode of hot Fox drama "The Following" promises to be an exciting one. For spoilers from actor Sam Underwood, who plays both twins Mark and Luke on the show, read on.

In a recent interview with TV Guide, Underwood discussed the dynamic between Mark and Luke.

"On the surface, [Luke is the leader], yes. But Mark also has a huge amount of power over Luke. You see that in the first episode when Luke is about to go all crazy on Carlos. Just before he's about to kill him, Mark kind of reins him in. ... He has the ability to be able to do that with Luke because of their relationship. Luke is the front-man of the band. He's the Paul McCartney. But Mark is the Ringo Starr. He's there keeping it all together, even though he's not at the very front," the actor said.

Underwood went on to say that Luke is perhaps the one fans should be afraid of.

"Purely based on the fact that Luke is the more impulsive one, doesn't always think before he acts, and is kind of a bit more of a rebel without a cause - or a rebel with a cause - I would say Luke's the more actively dangerous one. In a very broad sense, Luke loves to be seen, heard, celebrated for what he's done. He loves the spotlight, whereas Mark is a lot more reserved and thinks before he acts."

Underwood also teased a shift in the relationship between Mark, Luke, and Emma.

"You put three sharks in a tank together, I don't think they're always going to get on swimmingly," he says. "These are all highly dangerous, intelligent individuals, and no one trusts each other. ... It's going to play out in a very interesting way," the actor said.