Throughout the SeriesEdit
In Stakeout, Marcus is introduced to the precinct as Captain Holt's nephew and him and Rosa are instantly attracted. Through Holt, Marcus asks if Rosa is single and Rosa says that she is but if Marcus wants her number then he has to ask her for it himself. Rosa and Marcus begin a relationship but Rosa breaks it off due to awkwardness with Holt. Holt later says that they can work it out if Rosa wants to begin a relationship with Marcus.
In Beach House, Marcus buys Rosa a charger so that they can long distance text. They kiss and say goodbye. Later, Rosa accidentally hurts Marcus's feelings via text and asks Charles to help. Charles gets them back on track but tells Rosa that she needs to write the last text. She does and Marcus sends a shirtless photo. Rosa thanks, Charles and runs off to send one back.
In Boyle-Linetti Wedding, Charles asks why Rosa didn't bring Marcus and she doesn't want to rush things. Rosa later realises that she is a coward for not rushing into things and invites Marcus. Rosa and Marcus say they love each other and kiss but Charles interrupts the moment.
In Johnny and Dora, Marcus is the sole attender at Rosa's birthday party as he knows that she doesn't like big parties. He says that Charles is the one who advises him to rent the entire bar for Rosa. He realizes, however, that they should have kept the bartender as he doesn't know how to make drinks.
In Into the Woods, Rosa admits that she wants to break up with Marcus as he is so emotional. Holt helps her by advising her on how to do it without hurting Marcus's feelings. Rosa later breaks up with Marcus and Marcus gets emotional as well as confused when Rosa tries to sneak out of the window.
Marcus is the nephew of Captain Holt and the two appear to be on friendly terms. Marcus is shown to be friendly, thoughtful and very emotional (even crying at a commercial).
- Marcus is Rosa's first on-screen love interest.