Grey Sloan Memorial Hospital will be divided in the upcoming Season 12 installment of “Grey’s Anatomy.” And according to the synopsis for episode 21 of the ABC series, titled “You’re Gonna Need Someone On Your Side,” the separation will be caused by Callie and Arizona.

In the forthcoming installment, Calzona will each pull out all the stops in an attempt to win custody of their daughter Sofia (Eva Ariel Binder) — including forcing their scrub-donning friends to take sides.

“Arizona (Jessica Capshaw) and Callie (Sara Ramirez) are as odds and put their friends in the middle of an uncomfortable situation,” the summary says. Viewers have also been given a look at which pals Calzona will drag into their fiery feud in a sneak-peek video.

“I need someone who knows me and my kid. Someone who people trust with kids and, well, you’ve known me…” Callie says to Alex (Justin Chambers) in the promo. “I also know that you have a relationship with Arizona.”

“Are you asking me to take the stand for you for your custody?” he answers, leaving viewers on the edge of their seats. But Alex isn’t the only Grey Sloan employee Calzona is implicating in their custody battle. Callie will also reach out to Meredith (Ellen Pompeo), while Arizona seeks aid from April (Sarah Drew).

Amid the custody chaos, audiences can also expect to watch Stephanie’s (Jerrika Hinton) new relationship take a complicated turn while Meredith plays cupid. According to the synopsis, Mer will try to get Amelia (Caterina Scorsone) and Owen (Kevin McKidd) to make their longtime, on-again-off-again fling a permanent romance.

“Grey’s Anatomy” airs Thursdays at 8 p.m. EDT on ABC.