Grant Mitchell's secret son Mark Fowler Jr will cause waves in Albert Square as he demands answers about his family background.
Mark, played by Ned Porteous, appeared in the closing moments of Thursday night's show after receiving a phone call from Grant's brother Phil about his true parentage.
He arrived on the doorstep of his uncle Martin Fowler (James Bye) to the shock of fans in Thursday's episode, and on Friday he will demand the truth about his paternity from the Beales.
Despite Martin's surprise, viewers were very happy with the new arrival.
However Ian and Jane (Adam Woodyatt and Laurie Brett) already know the explosive secret that Mark is the product of a one-night-stand between his mum Michelle Fowler (Susan Tully) and Grant (Ross Kemp).
With Ian adamant that Mark doesn't find out, will they be able to hide the truth from him?
Viewers watched Grant leave the show earlier this week, but Ross has confirmed he will be back for more episodes in September.