When the leader of a local street gang abducts Holmes to compel him to find the person responsible for a hit on his men, Holmes and Watson get caught in the middle of an international hunt to recover a centuries old, priceless artifact. Also, Watson debates whether a personal favor Shinwell asks of her is outside her comfort zone.

Season 5 ends with Holmes and Watson pursuing an elusive criminal as a gang war erupts in New York City. While the NYPD works to contain the violence, the two investigate the murder that appears to have ignited the city-wide conflict and discover that a familiar face is pulling the strings.

After an explosion at a traffic stop, Holmes and Watson must determine whether the attack was a terrorist attack; Holmes and Watson suspect there is more for them to discover regarding the recent attack on someone within their inner circle.