By Michael Ausiello
Updated December 11, 2008 at 12:00 PM EST

Come February, Sam may be wishing she had climbed aboard that booby-trapped ambulance after all.

Sources confirm to me exclusively that Shannon Woodward, best known as Eddie Izzard and Minnie Driver’s burgeoning scam artist daughter on The Riches, is joining ER in the recurring role of Kelly, estranged younger sister of Linda Cardellini’s Sam.

Per an ER insider, Kelly shows up on her sib’s doorstep with some horrifying news: she wants to move their ailing mother to Chicago so Sam can care for her for a change. Wait, it gets worse. Fifteen years ago, Mom kicked a then-pregnant Sam out of the house with nothing but the clothes on her back, and the two haven’t spoken since.

Again, death via exploding ambulance? Not looking so bad!