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Cristina (Sandra Oh) may be cutthroat and ambitious, but at least she realizes that there are some rules you have to follow in medicine — a lesson intern Leah (Tessa Ferrer) hasn't internalized yet.

In this sneak peek of Grey's Anatomy Season 9, Episode 13: "Bad Blood" (January 31), Cristina and Leah are faced with a unique surgical challenge when they're forced to operate without blood due to a patient's religious beliefs. But it looks like Leah is on the verge of rebellion.

Check it out below.

Catch the episode tonight, January 31, 2013, at 9 p.m. ET/PT on ABC.