I Will Follow You Into the Dark

Summary

Derek decides to quit after learning that more of his patients have died than survived; Izzie's interns make an unsettling discovery about "Patient X."

Guest stars

• Jessica Capshaw as Arizona Robbins
• Loretta Devine as Adele Webber
• Gloria Garayua as Intern Graciella
• Mark Saul as Steve
• Wendy Hoopes as Tricia Shelley
• Erin Cahill as Megan Shelley
• Michael Rady as Michael Shelley
• Candice Afia as Intern Laura
• Nicole Cummins-Rubio as Paramedic Nicole
• Molly Kidder as Intern Megan