'Vanderpump Rules' : Tom Schwartz Doesn't Remember Allegedly Cheating on Wife Katie Maloney

Infidelity is the running theme on this season of Vanderpump Rules — then again, when isn’t it?

On Monday night’s episode, Brittany Cartwright, Scheana Marie, Katie Maloney and Stassi Schroeder are living their best lives the morning after their “F— Jax” sleepover/Witches of Weho coven gathering, Postmates-ing a breakfast of Taco Bell and beer.

Hot sauce can’t fix all their problems, though: When Katie hears that Scheana is traveling to Las Vegas on a private jet with Lala Kent, she disses the newly reinstated hostess’s “sugar daddy married boyfriend.”

“He’s not married,” Scheana insists.

“Anymore?” Katie shoots back.

(For the record, Lala has been linked to Hollywood producer Randall Emmett, who reportedly finalized his divorce from actress Ambyr Childers this month.)

But the women put on a united front when Jax Taylor walks in, griping about his “trashed” apartment and accusing the”firing squad” of riling up girlfriend Brittany in the wake of his cheating scandal.

“You’re making it like it’s the end of the world. And you’re not that devastated,” he says. “You’ve been partying everywhere, you’re not that devastated.”

Brittany jumped up, cursing and smacking him around into another room, where they continue screaming at each other.

“Everything was fine until you went to that damn party, and then those girls just filled your head … they’re insecure about your own issues, they’ve got to put it on you,” Jax yelled.

WATCH: Jax Taylor Admits He’s Seeing a Life Coach After Cheating on Girlfriend

Later, Scheana meets up with Ariana and Lala to fill them in on the drama.

“Katie also did make a comment about your boyfriend again,” she tells Lala, who freaks out — and drops a bombshell.

“All right, let’s talk about married people cheating. Your man made out with my friend! Why don’t you worry about your own god—- marriage and stop worrying about my man, who is very much not married, who has been my boyfriend for a year?” she yells, as Ariana Madix and Scheana, stunned, ask her to rewind and “back it up.”

Lala claims that, while Katie was away in New York, Schwartz got “hammerd” and made out with her friend Allie, whom he drunkenly called “Bubba” — his overly cutesy nickname for his wife.

‘She is not safe anymore,” Lala declares. “You f– with my relationship, I am coming for you first.”

Ariana decides to talk to Schwartz that night at SUR co-owner Guillermo Zapata’s party, so Katie can “hear it from her husband, not the rumor mill.”

Meanwhile, Stassi flawlessly plans Guillermo’s birthday, Jax and DJ James Kennedy dutifully stay away from SUR to get weird with absinthe, and things are looking good for Tom and Tom at TomTom — until Schwartz’s alleged infidelity threatens his marriage and partnership with Lisa Vanderpump.

When Ariana pulls Schwartz aside and repeats the story, he acts dumfounded.

“There’s no way. No, it couldn’t have been,” he slurs. “Yeah, I remember going to Bungalow, but I definitely don’t remember making out with anybody. I got s—faced that night, I remember that, but … ”

For Ariana — and all of us — it’s déjà vu. At least twice, Schwartz has hooked up with girls and feigned ignorance before coming clean to Katie … but that was before they wed.

“I truly and honestly am baffled,” Schwartz says in a confessional. “Obviously I’ve done this before, so I am capable of this, but I have no recollection whatsoever of it. I’m like a werewolf.”

“Go home and tell her in the privacy of your own home, Ariana advises.

Naturally, he doesn’t. Clearly buzzed, he complains to Katie about getting “reamed” by Ariana, and the whole story comes out. Katie remains stone-faced inside the party but breaks down outside in the alley, like so many SURvers before.

The girls’ question Lala as a reliable source, but as Stassi says, “Usually with this group, where there’s smoke, there’s fire.”

Schwartz comes outside and asks her to calm down, which, spoiler alert to men everywhere, never ends well.

“Things have been nothing but good between us, but you can’t stop making out with people that aren’t your wife. What the fuck is wrong with you? You need help,” Katie cries.

“I have already been down this road with Tom cheating on me,” she adds to the camera. “I feel like this is just come kind of bad dream.”

Back inside, Tom digs himself into an even deeper hole, recounting what happened to Lisa, doing his best to laugh with that signature Schwartzy-poo charm: “I know, it’s so embarrassing.”

But Lisa is pissed. She officiated his marriage — was it a sham? — and now, she’s questioning whether he’s a trustworthy business investment.

“Am I going to come in the night after and he’s going to be wasted, lying on the couch, with all the money gone and the keys on the pavement and he’s going to say, ‘Well, I don’t remember’?” she wonders.

Vanderpump Rules airs Mondays at 9 p.m. ET on Bravo.