When Alex's father needs a new kidney, an unlikely donor emerges and family secrets threaten to destroy the close relationship between father and daughter.

In the season finale of "Heartbeat," Alex fights to save the lives of Jesse, Pierce and Ji-Sung when a mysterious and deadly illness sends the hospital into lock down. Meanwhile, Millicent must pick up the pieces when Alex disobeys the orders of the CDC, and an elderly man searching for his missing wife leads Alex to make a drastic decision in her love life.