The medical drama returns as Mo's surgical skills and emotional resilience are pushed to their limits by a reunion with her surrogate son William and old friend Sorcia, who require her help. Jesse shadows Sacha for a day to learn the role a surgeon plays on Keller, but Guy is quick to question his motives. Plus, Cara tries to track down the mystery hero who saved an octagenarian patient from drowning, even if it risks the wrath of Raf.