05/05/2014 at 01:30 PM EDT
While Dean McDermott
cheated on her in Toronto, Tori Spelling
was celebrating the holidays with their children.
The revelation brings Spelling to tears in the upcoming episode of True Tori
– and seems to lead McDermott to an emotional breakthrough about his infidelity
"We were at a Christmas event. I was taking pictures of the kids in fake snow," Spelling, 40, tells her husband in a clip. "I had all four kids there by myself, managing them, and you called me, and we talked to you on FaceTime. And I was like, 'Oh, Daddy's busy, he's working.' And this is the memory I have of that Saturday."
As she continues, McDermott , 47, winces in pain, describing the feeling as "like an ice pick through my head."
"I feel shame. I've never felt shame before," he says through sobs. "You were at a Christmas event, and I was f––king around. That's disgusting. That's disgusting."
airs Tuesday at 10 p.m. ET on Lifetime.