When a driver for a ridesharing company is intentionally run over by a city cab, Holmes and Watson wonder if it’s a case of professional jealousy. A casual romance Holmes has with one of his longtime "Irregular" consultants becomes complicated when the woman makes a shocking request.

When a serial bomber becomes active again after being dormant for six years, Watson seeks help from Shinwell Johnson, a former patient whose life she saved when she was a surgeon. Also, Holmes senses Watson is unhappy and questions whether she is still fulfilled by her detective career.