Kat Moon is left "really conflicted" after trying to reconcile with husband Alfie.
The 'EastEnders' character - played by Jessie Wallace - has been indulging in an affair with a mystery person for some time, but after trying to get back on track with Alfie (Shane Richie) the lover texts her making grand proclamations about their relationship.
A source told InsideSoap magazine: "Kat tells Alfie she'll organise a special night for them, and that it will be worth the wait.
"But while she's making these romantic plans, the fella she's been sleeping with texts her, claiming Alfie can never make her as happy as he would. It leaves Kat really conflicted."
Although the mystery person has not yet been revealed, Tony Discipline - who plays Alfie's cousin Tyler Moon - has previously hinted they may not even be male.
He said: "To be honest I don't know. It's a secret, nobody knows it. It could be a man, it could be a woman. It's Albert Square!"
Among the names suggested for the person having an affair with Kat are Michael Moon, Max Branning and Jack Branning.