If you thought the Walkers had issues on Brothers & Sisters, wait until you see the Laurents in action.

"They may put the Walkers to shame," Gilles Marini, who plays Luc Laurent, tells TVGuide.com. "It is just pure drama, through and through. There's no other way to describe it. I don't think the Walkers have even dealt with something or someone like that before."

That "someone" is Luc's mother, Gabriela (Sonia Braga), a life-of-the-party former screen siren who unexpectedly drops by Sunday's episode to visit her son and his new fiancée Sarah (Rachel Griffiths). Except she's not exactly welcome, as mother and son have been estranged for years.

They do, however, pick up right where they left off: yelling at each other in French. "He cannot be in the same room with his mom just because of what she's done in her life to him," Marini says. "What she did was bad. He thinks she's selfish. Luc just does not accept the way she is.

"You've never seen Luc upset," he continues. "Upset is a small word for what's going to happen. He's crushed and destroyed from the inside out."