Fans of the soap were left on tenterhooks last week trying to guess the identity of a mystery woman who was accidentally locked into the Dingles' barn.
By Thursday it was revealed that the woman was in fact Faith (played by Sally Dexter), the mother of Cain (Jeff Hordley) and Chas (Lucy Pargeter).
Viewers will remember that Zak (Steve Halliwell) had an affair with Faith, his brother Shadrach's wife, over 40 years ago, which resulted in the birth of Cain.
With Zak's history of cheating, Lisa (Jane Cox) begins to worry next week that her ex-husband will stray again.
Emmerdale: Will Zak Dingle have another affair with former flame Faith?
Emmerdale: The mystery woman in the barn was revealed to be Faith last week
Her fears are realised when Faith begins flirting with Zak in front of her.
Wracked with guilt over Joanie's death, Zak has been acting oddly and snapping at Lisa.
Later on, a worried Lisa admits to her daughter, Belle (Eden Taylor-Draper) that she thinks Zak is having an affair.
Emmerdale: Lisa Dingle's birthday ends with an almighty row
Emmerdale's most shocking moments
Thu, January 5, 2017
Emmerdale's most shocking moments: Explosions, car crashes and murder – life in the Dales is never dull. Here are the most dramatic scenes from the popular soap.
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Emmerdale's most dramatic moments
In scenes set to air on Thursday, the drama comes to a head at Lisa's birthday party in The Woolpack.
Thinking she has heard Faith make a play for Zak, Lisa storms over and an almighty row erupts.
Has Lisa got it all wrong? Or has Zak been unfaithful yet again?
Emmerdale continues tomorrow night at 7pm on ITV