Grey’s Anatomy’s McSteamy is heading for a Private Practice crossover during its newest season and if you are a fan of Mark and Lexie’s relationship, then you may not be pleased to hear that the visit means more than one problem for the cute couple.

Mark contacts his ex-girlfriend Addison to make a visit to Seattle Grace and later follows her up to LA, as he needs her to operate on one of his patients.

Problem number one: Mark and Addison get closer again.

“They’ve both really grown up since they were together, and most of the animosity that they had is gone,” Shonda Rhimes, executive producer of both Grey’s and PP told EW.com. “Now they’re friends, but they may end up falling back into their old patterns while they’re together.”

Problem number two: The mysterious patient may be Mark’s long lost (and now pregnant!) daughter.

Former Sarah Connor Chronicles actress Leven Rambin will play the role of Mark’s patient and possible daughter and of the new character Rhimes acknowledged that she would present a “new obstacle for [Mark and Lexie]… I’m not sure it’s the kind of obstacle people are expecting, but it’s definitely a new one. I’m not sure they’ll stick together through it.”