Things become more strained than usual between Burke (Isaiah Washington), who has been offered the position of chief surgeon, and Cristina (Sandra Oh), who is still keeping Burke's tremors a secret. Elsewhere, Meredith (Ellen Pompeo) must bite her tongue to keep several secrets from her half-sister Molly (Mandy Siegfried), who has been admitted as a patient. George (T.R. Knight) senses his father's vulnerability for the first time when the elder O'Malley (George Dzundza) undergoes surgery. And Mark (Eric Dane) and Derek (Patrick Dempsey) must cope with conjoined twins (Jason Sklar, Randy Sklar) who refuse to be separated despite the consequences of not doing so. ~ Hal Erickson, Rovi