In this sneak preview clip, Bachelorette host Chris Harrison explains that it is there when single mom Maynard, 26, learns race car driver Arie Luyendyk, Jr., had dated show producer Cassie Lambert in 2003.
Calling Luyendyk and Lambert's relationship "brief," Harrison then shows footage of Maynard calling herself an "idiot" for not seeing through her suitor's duplicitous behavior.
"If he's OK with hiding that he even knows you -- much less dated you -- and we've been hanging out for so long, what else is he hiding?" Maynard fumes in a conversation with Lambert. "He's a good actor!"
When Lambert admitted that she and Luyendyk weren't that close, Maynard seethes. "It wouldn't have been weird if someone said on day one: 'We know each other.' I wouldn't even care, but now I feel like an idiot," she says. "I know something about Arie that he's not telling me."
Though Maynard's conversation with Lambert was somewhat calm, a source tells Us Weekly ABC's leading lady was "livid" upon hearing the news, and took her anger out on Luyendyk. "She cut him right then and there," the insider explains. "Her ego was shot."