Pratt is overwhelmed when his developmentally disabled brother, Leon (recurring guest star MARCELLO THEDFORD), persuades him to treat a gravely wounded robber who duped Leon into participating in a crime. Carter stuns Abby by deciding to go to Africa, where the medical needs are greatest. Meanwhile, Carter attends to the sickly Dr. McNulty (recurring guest star ED ASNER), the curmudgeon he recently met who runs a storefront medical clinic.