Cristina and Preston have philosophical differences over a young boy who needs a heart transplant; the interns help Alex prepare for his exam re-sit; Meredith reminds Izzie about the true meaning of Christmas.
Allison is called upon to help Devalos solve the murder of one of his friend's sister, but her visions keep pointing to the friend's first husband, who died in a car crash two years earlier.
Billie's parents have an unconventional stay with their daughter when she inadvertently transforms them into cold-blooded assassins. Phoebe has a case of writer's block.
Williams discovers the Nation of Islam and starts trying to change her ways, attempting to change several other deputies along with her.
Natalie pursues a case while Monk is sick in bed with the flu.