"David isn't one of us."
―Marcy Warton (Traveler 3569)[src]

David Mailer, played by starring cast member Patrick Gilmore, is Marcy Warton's social worker. He has not had his mind overwritten by a traveler consciousness as of the end of the second season.

He is a social worker who looks after more people than he officially has to. One of whom is Marcy and many of whom are homeless. He truly cares for them, which means that he often buys them things out of his own pocket and spent all the money that he won in the lottery on things for them.


He had been looking after Marcy for about a year prior to her being overwritten by Traveler 3569.

He first met the Traveler 3569 after going to see Marcy for an arranged meeting. He worries because he sees the cut on her head from where she fell and so takes her to the doctor. David takes Marcy on the bus and wants to get her to read. While pulling out a children's book, Marcy begins to read the newspaper which surprises David. He believes that it's some kind of medical miracle that Marcy no longer has intellectual disabilities, though the doctor believed that it was more likely that she faked the disability and that the head injury made her forget who she was pretending to be. He allows Marcy to stay with him after having a seizure. (Travelers)

David wants to take Marcy to the hospital but she refuses, knowing what's happening to her. He gives her a phone and calls her when he sees the plane crash that she'd predicted, but writes it off as FBI buisness. (Protocol 6)