When the show's new star gets stuck in Cuba, Derek puts Karen in as understudy; Tom and Julia celebrate their anniversary.

Karen finds herself seduced by the glamorous life of new BFF Rebecca Duvall -- but can Rebecca be trusted? What will Karen's ascent mean to her relationship with Dev? And will Rebecca drive Derek insane? Eileen introduces new beau Nick to ex-husband Jerry, while Julia panics when her son Leo goes missing.