The actor began treatments for Hodgkin's lymphoma last year (09) but he and wife Jennifer Carpenter, who plays his adopted sister on the hit series, refused to worry the rest of the cast with the health scare, according to co-star Lauren Velez.
She tells E! Online, "You know they've always been incredibly private and kept to themselves, and he's always been very private and throws himself into his work, so I knew nothing of it, and I don't think anyone else did either."
Hall stunned fans after revealing on Wednesday (13Jan10) he has been battling cancer and is now in remission.
The Dexter cast and crew are set to return to work on the next series in May (10).