As the high school's Winter Ball approaches, Mariana and Jesus fret about dates and a surprise nomination for Winter Queen raises suspicions. Zac's mom (guest star Romy Rosemont) shows up at school to talk to Lena. An old friend pays a visit to Callie wanting to make amends, and Brandon feels threatened. But a past mistake could cause Brandon to lose Callie for good. Ana returns with unsettling news for Stef.