Grey's Anatomy: Season 4, Episode 2

4 - 2: Love/Addiction

An apartment explosion inundates the ER with patients, and Alex jeopardizes a family when he realizes the cause of the accident. Meanwhile, Meredith intrigues Derek with an "S&M" approach on their relationship, and Derek gets the wrong idea. Cristina is frustrated when Mama Burke returns and she wants all of Burke's old things.