Stephen Tyrone Williams

Holmes and Watson investigate the murder of a hedge fund manager who was running a Ponzi scheme; Sherlock considers sponsoring a fellow addict.

When Shaw is tasked to stay close to a 10-year-old (guest star Danielle Kotch) identified by The Machine, she grudgingly develops respect for the young girl's skills in surveillance and realizes it could be the very reason why the girl's number has come up. Meanwhile, Carter's mission to bring the criminal organization HR to justice risks exposure.

Joan discovers an unsolved murder connected to a rare prehistoric fossil when she reviews one of Sherlock's cold cases; Sherlock's responsibilities as a sobriety sponsor cross personal boundaries.