But will he keep their secret?
FOR WEEK COMMENCING 18TH MARCH
After Denise's ultimatum, Jack is walking on eggshells around her and confides in Stacey who advises him to do whatever she asks.
Later, Stacey goes to see Denise and persuades her to get her marriage back on track and they arrange a family barbecue to bring both sides of baby Charli's family together.
At the barbecue, things are awkward and Stacey feels terrible as she talks with a fragile Denise.
Out in the backyard, Stacey tells Jack that she wishes she could be selfish, but he needs to be there for Denise.
Holding his arms out for a hug, they share a tender goodbye kiss, but Martin walks in and catches them. As Jack and Stacey insist that the kiss was a moment of madness, they beg Martin to not tell Denise. But when Chelsea interrupts, she's suspicious when Stacey rushes after Martin.
When alone, Stacey admits to the affair with Jack and tells Martin it's over and the whole thing is none of his business.
Later, when Martin confides in Kathy over what's happened, she desperately tries to persuade him to keep the secret, fearing the consequences of Denise finding out for the rest of the six women.
Back at the Brannings, Jack breaks down to Denise about how scared he's been about her, leading to a breakthrough for them as a couple as they pledge to fix things.
EastEnders continues Mondays to Thursdays at 7.30pm on BBC One with first look episodes available from 6am on BBC iPlayer