This Is Us Sneak Peek: We're Totally Worried About Kate and Toby

Exclusive: Resentment grows between our favorite lovebirds when one's weight loss success begins to outpace the other's in this clip from the NBC hit's next episode

It looks like lovebirds Kate and Toby are due to hit another bump in the road, This Is Us fans.

In this sneak peek of tonight's all-new episode, exclusive to E! News, the couple show up for weigh-in day at their weight loss support group and, despite all her hard work, the results aren't exactly what Kate (Chrissy Metz) hoped for. Making matters worse? Toby's (Chris Sullivan) just shedding the pounds like it's no big deal.

"I kill myself for weeks and I'm down a pound?" she asks, incredulous at her results.

"And a quarter," Toby adds, not really helping matters.

When it comes time for Toby to step up on the scale and he gets the good news that he's dropped eight pounds like a bad habit and hit his goal weight, well, the look on Kate's face says it all. Will the fledgling couple be able to survive the clear resentment brewing on Kate's end? We'll have to tune in to find out.

Elsewhere in the episode, look forward to the dynamic of Kevin (Justin Hartley) and Randall's (Sterling K. Brown) rocky relationship finally getting an explanation. Also, as Rebecca (Mandy Moore) gets back to work for the first time in years, she and Jack (Milo Ventimiglia) acknowledge the distance between them. Plus, a secret that William (Ron Cephas Jones) has been keeping will unexpectedly come to light as he and Beth (Susan Kelechi Watson) spend time together.

This Is Us airs Tuesdays at 9 p.m. on NBC.

(E! and NBC are both part of the NBCUniversal family.)