In "Lost in the Flood," the next episode of "Arrow," Felicity will join forces with her estranged father, the Calculator (Tom Amandes), as well as Curtis Holt (Echo Kellum) in order to put an end to H.I.V.E.'s plan. Of course, when her mother Donna (Charlotte Ross) finds out, she's none too thrilled at the idea of her daughter working with her ex, and the turn of events will force her to reveal something about her past with the Calculator that may threaten her present relationship with Felicity.
"Felicity has asked for her father's help in dealing with a crisis in Star City -- she kept it a secret from Donna because she knew how I would feel -- and obviously, when Donna finds out that he's anywhere near my daughter, a lot of suppressed emotions come spewing out," Ross revealed to TVLine.
"Donna has said that he left when Felicity was very young, and Donna hard a hard time financially, working three jobs to put food on the table," she continued. "So while we've alluded to the fact that Noah was very bad, to what degree and what he did specifically will be revealed a bit this week."
"There is something that Donna has kept hidden for many, many years and she decides to, finally, come clean to Felicity about it -- even though she knows she may risk losing her by doing so," she teased.