Harvey got involved with Charles Forstman due to Marcus asking for money for his second chance, a restaurant. As of "Not Just a Pretty Face", he doesn't know that the money had been dirty.
He appears in flashback in "Faith" when Harvey is telling his therapist about his parents. He blamed Harvey for destroying their family.
He appears in "The Painting" at his father's funeral in flashback and has the first appearance in the present. He threatened Harvey after admitting that Lily was there and would say a few words. He tells Harvey that it was time to let it go.
After Harvey approached him in the present, he invited him to stay at Marcus' home with his family.
During the events of Suits LA, it was revealed that he had cancer again and unfortunately succumbed to it.
Trivia
Marcus' phone number is 617-665-0138.
He has a daughter who likes Pinkalicious.
Marcus had been sick where he needed chemo twice in his life: once when Harvey was younger and once when Harvey wasn't speaking to his mother.
