As Ming gets ready to proceed with her plans for artificial insemination, her husband Chen, is stressed and fantasizing about street races and infidelity. The sperm donor, Fitz, their medical school classmate and Ming's former boyfriend, is considering reinstatement at the hospital which stirs up a lot of unresolved issues. His return would also create more tension between the trio since he wouldn't be an absentee donor after all, but working alongside the couple every day.

Fitz and Ming talk about their imminent insemination plans. Fitz tells her that since he's decided to stay in Toronto and work at Mercy, he'll understand if she changes her mind. But she still wants to go forward even though she knows it will be uncomfortable for everyone. Their plans incite the doctors to reflect back on their early days as residents in the hospital and and the professional and romantic rivalries that took root.

As Fitz and Ming debate the merits of their insemination plans, the doctors revisit their past entanglements. Fitz finds himself challenged by the demands of a psychotic patient. Chen is called away to Brisbane to visit his dying grandfather. And Ming comes to terms with her surprise pregnancy and what it means for her future.

It's Christmas Eve, and chaos reigns in the emergency room. Fitz contends with some hard-assed cops and a belligerent patient. It's a contentious situation that he initially handles well, but as the evening progresses he spirals out of control to a very self-destructive place. When Chen finds himself dealing with a family of a man who died in a brothel, he starts to question his own views on medicine and family. Meanwhile, though she's not embroiled in the turmoil of the hospital, Ming is confronted by her father's strange solution to her fertility problems.

After Fitz takes a sick patient from China to Toronto who dies later, he is diagnosed with a mysterious respiratory illness. He is immediately put into isolation, but has infected Chen who examined him. Ming is in quarantine at home where she starts to rethink again about adoption. Bearing the scars of never knowing her father, she doesn't know if she wants to make a child go through that situation again.