Peter Gallagher, best known for his roles in The O.C. and Law & Order: SVU, will be joining the cast of Grey's Anatomy in a recurring role as Dr Alan Hamilton in the upcoming 18th season. He will make his debut in the season premiere, which airs on September 30th, and may hold the key to the reintroduction of a familiar face from Meredith's past. The news follows the announcement that Kate Burton, who plays Meredith's mother, will also be making multiple appearances in the new episodes. With a crossover with spin-off show Station 19, season 18 is shaping up to be an action-packed hour of TV.