Arizona's leg was heavily infected after the crash. Her doctor in Boise recommended that they amputate her leg, but Arizona withheld consent, and demanded to be taken back to Seattle, where Callie was.
In Seattle, Callie and the other doctors tried to fight the infection. As they waited, Arizona got increasingly freaked out, until she broke down and made Callie promise to not cut off her leg. She also displayed huge personality changes, including lashing out at Alex (Justin Chambers) in a very cruel way, making Callie worried that if she lost her leg she'd be even worse.
So Callie came up with an ambitious plan to save the leg, and convinced Owen (Kevin McKidd) to let her try. But before they could go into surgery Arizona started crashing because of the infection, and Callie made the call to cut off her leg to save her life.
And the person who actually operated? Alex.
Talk about a complicated, heartbreaking situation. One thing's for sure: This season is going to be interesting.
Grey’s Anatomy airs Thursdays at 9 p.m. ET/PT onABC.
Rebecca Martin is an editor at Wetpaint Entertainment. Follow her on Twitter @BeccaMartin47.