Steph - played by departing actress Carla Bonner - has been misleading her loved ones for months in a bid to conceal the fact that Dan Fitzgerald is the father of her child. The mechanic has staged a sham reunion with ex-boyfriend Jarrod 'Toadie' Rebecchi (Ryan Moloney) to protect the secret.
However, speaking on Live From Studio Five last night, Fletcher confirmed that the truth will come out later this year.
The actor - who portrays Karl Kennedy - explained: "This has been brewing. The whole street will be torn apart by this. It's a big, big, big drama."
Fletcher also offered teasers for the soap's forthcoming 6,000th episode, which is to be the highlight of its 25th anniversary year.
He said: "We've just shot it. Something rather unpleasant happens to one of our iconic characters. I'm involved with the more pleasant side, which has kind of already been alluded - there might be a wedding in the air."
> Neighbours boss teases 6,000th episode