The furious mother and her ex boyfriend Paddy Kirk confront Robert and tell him to stay away from Aaron.
Following Katie's shock death at the farm, Robert agrees, uncertain how much Chas and Paddy know.
Katie fell through unstable floorboards at the farm, after catching Robert and Aaron kissing, crashing to her death.
She had planned to show Robert's wife-to-be Chrissie what he'd been getting up to behind her back.
Viewers watched Robert go ahead with his wedding to Chrissie, telling Aaron an edited version of what happened at Wylie's Farm.
Chas is convinced Katie's death was not an accident and begins to suspect Robert, to Aaron's horror.
A source told the Daily Star: "Robert feels terrible Katie is dead. He can't bring her back and he has to live with his part in it all for the rest of his life.
"Chas demands that he meet her. She wants to know exactly what's been going on with Aaron and she takes Paddy along for some moral support. Paddy knows Aaron has been having an affair but had no idea it was with Robert.
"When they ask him to stay away from Aaron he agrees but it remains to be seen how long they can keep their secrets."
Robert's showdown with Chas and Paddy will air on ITV this Thursday.