Eps9greys Anatomy - Season 1 -

The woman turned her gaze to Meredith, her eyes sharp. "And you must be the woman who's been sleeping with my husband."

: Addison Montgomery-Shepherd arrives, revealing Derek is married. Eps9Greys Anatomy - Season 1

: Derek operates on Chief Webber's brain tumor in secret. The woman turned her gaze to Meredith, her eyes sharp

Watch a recap and review of the intense season 1 finale where secrets are finally brought to light: Watch a recap and review of the intense

Meredith Grey spent the day feeling like her relationship with Derek Shepherd was finally on solid ground. They had survived the initial awkwardness of their secret romance and the pressures of the internship. But at Seattle Grace Hospital, peace was always temporary. A syphilis outbreak had swept through the staff, forcing the Chief to hold a mandatory—and humiliating—meeting about sexual health. George O’Malley was the most public victim of the "syphilis train," having contracted it from Olivia, the nurse who had caught it from Alex Karev.

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.

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