Arlene Tur

Someone from Derek and Addison's past arrives in Seattle and shakes things up. Meanwhile, Burke learns about Christina's secret and, after a visit with her mother, Meredith looks into more of her family's dirty laundry.

When a government witness is murdered, the FBI hires Cal and co to determine who was responsible for leaking the victim's whereabouts. The team are also tasked with keeping Agent Reynolds, who is key to closing the case, out of harm's way. However, suspicions are aroused when Reynolds refuses to testify.