Brittany spoils Jax on his 38th birthday, but he shows his lack of maturity when confronted with a reminder of his infidelity. Seeking revenge on Jax for telling people Rob doesn't love her, Scheana sets Brittany up with SUR's hottest new model and bartender. Ariana's brother asks out new SUR hostess Billie Lee, but when Stassi questions Jeremy's character, Ariana responds with fierce sisterly protection. James has an emotional reunion with his Dad, and Sandoval and Schwartz must redeem themselves with Lisa after a disastrous Vegas business trip.

The Mexico adventure continues as the group explores a natural water park, Playa del Carmen nightlife, and a little local spot called "SUR." James tries to remain in Jax's favor by exposing Scheana's role in hooking up Brittany with the hot new barback, Stassi and Kristen clash over Kristen's vacation meltdowns, and Lisa predicts that a volatile romantic triangle at SUR will end explosively.