Ghostwriter had to go back in time and help him and Catherine clear his name with the help of the team because he thought it would help save history & the team. He was right, because while the case was going on, mysterious things happened: an old newspaper article which talked about the crime and the capture of the real crook started to fade away and Reggie (Jamal's father) started to get sick. Eventually, Frank, Catherine and the team solved the case. The real robber was sent to jail, Frank stayed with his foster family and Reggie was a healthy man again.
Frank grew up to be a pediatric heart surgery doctor, dedicating his life to help those who couldn't afford medical care, and he was the one who saved Reggie's life when he was four years old. That is why the future of the team and history was hanging in the balance; otherwise Reggie would have died and Jamal would never have been born.
Frank passed away just before the series began, but was survived by his best friend turned wife Catherine.