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 The Lightman Group to determine who leaked the witness' whereabouts to the killers and to protect Agent Reynolds, the star witness in the case. When Reynolds refuses to testify in the case, Lightman and Foster learn he is hiding something in his past.