Brendan is taking centre stage in this year's run of the E4 spinoff, as he features in a dark storyline with half-sister Cheryl, their Nana Flo, bad boy Walker and troubled Joel.
Show bosses have promised that the episodes will provide an insight into the Brady family history - partly through flashbacks to Brendan's childhood.
Scanlan told All About Soap of the flashback scenes: "They reveal why Brendan's the way he is - it's the missing piece of the jigsaw puzzle.
"Ever since he arrived in Hollyoaks two years ago, there have been questions about his murky past and now we'll get the answers. The truth is shocking and brutal."
The actor also confirmed that Cheryl (Bronagh Waugh) will be shocked by the actions that Brendan is driven to in Later this year.
He said: "Let's just say that what Cheryl sees Brendan doing is so dark it changes everything between them. Cheryl would never report Brendan to the cops, but she's so disgusted that she disowns him. I'm not sure their relationship can ever be repaired."
Discussing the big explosion featuring Brendan at the end of the series, Scanlan added: "I don't think it would be a fitting way for him to go. He needs redemption - he needs to sacrifice himself. You never know, though. This could well be where the journey ends."
Hollyoaks Later returns to E4 on Monday, September 17 at 10pm.