After bumping Lily’s head on the doorframe, Mitchel calls his sister for reassurance. Claire lets Mitchell know it’s fine because her youngest son was hit on the head a lot and he’s fine, but that correlation ends up worrying Mitchell more.
Mitch gets sick on his honeymoon, but spreads it to everyone else in the family. Each member goes through the pain they endured because Mitch didn’t quarantine himself. Only later in the episode do they find out that Mitch isn’t patient zero.