Marcus Diamond is a former Baltimore police officer who was shot 3 times in the line of duty and survived with the help of Johann Maelzel's Metronome, as revealed by Mrs. Frederic in "Stand". He was able to survive the most painful deaths with the help of the metronome. He is an associate of Sally Stukowski. They are both employed by Walter Sykes who is working against the Warehouse in Season 3. He was introduced in "Love Sick" when he is shown driving the young slacker/hacker responsible for unleashing the artifact-enhanced computer virus away from the scene, to a meeting with his employer.