As the shift ended, a heavy Seattle rain began to fall. Meredith and Derek stood near the hospital entrance, ready to head home together. Their conversation was light, filled with the easy intimacy of a couple falling in love. But the doors swung open, and a woman in a perfectly tailored coat walked in. She was striking, confident, and carried an air of authority that stopped them both cold. "Derek," she said, her voice steady.

The season one finale of Grey's Anatomy , titled "Who's Zoomin' Who?," originally aired on May 22, 2005. The episode is famous for its massive cliffhanger: the arrival of Addison Montgomery, Derek’s secret wife.

: Addison Montgomery-Shepherd arrives, revealing Derek is married.

The episode ended on Meredith’s shocked face, leaving fans to wait months for the fallout of the revelation that "McDreamy" was actually a married man. Key Storylines from the Finale

Derek froze, his face draining of color. "Addison. What are you doing here?"

: Izzie and Cristina risk their careers to find the truth about a patient's death.