Also known as: Throat cancer
Caroline is a young patient with an extensive throat tumor requiring vocal cord preservation. The episode centers on Jackson and April's attempt to perform an innovative throat transplant, which becomes impossible when the donor is lost. They ultimately perform a groundbreaking procedure using Caroline's own intestinal tissue to reconstruct her larynx and preserve her voice.
Also known as: Brain death
Brian is a 10-year-old boy who suffered a catastrophic injury while skiing on his birthday. He is declared brain dead and his father must be convinced to donate his organs. A lesion found on Brian's throat ultimately disqualifies him as an organ donor for Caroline's transplant.
Also known as: Severe flu
Zola has the flu, which prevents Meredith from traveling to Montana with Jackson, leading to April going instead. This is a plot device rather than a major medical storyline.