We finally know what went down between David (Johnny Galecki) and Darlene (Sara Gilbert) in the 21 years that Roseanne had been off the air. When we last saw them at the end of Season 9, the newlyweds were raising their infant daughter in Chicago while also frequently visiting Roseanne and John in Langford.

Tuesday's episode, titled "Darlene V. David," saw David return home just in time for Harris' (Emma Kenney) birthday after being away for quite some time. It turns out that he and Darlene are still technically married, though they've been living separate lives. While Darlene had been raising both of their kids in Chicago, David was off building homes for the needy in third-world countries. His lengthy absences put a strain on his relationship with his wife and kids, and he returned home to rectify that. Well, that and marry some woman named Blue who he met during his travels.

However, the long-awaited reunion stirred up old feelings between the high school sweethearts and it's not long before they're back in each other's arms, pledging to give their relationship another try. Their hookup also inspired David to admit his real reason for skipping town: the devastating loss of his older brother, Mark (played by the late Glenn Quinn).

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"When I left you and the kids, I rationalized that it was OK because I was helping people," he explained to Darlene. "The truth is, I left because my brother died and I was overwhelmed with all the responsibility and I just ran."

Later, Roseanne revealed that was just another one of David's excuses and that his actual reasoning had everything to do with his failing relationship with Darlene. Unable to handle their frequent fighting, he chose to run away instead of facing things head on.

While Darlene quickly forgave David for abandoning their family, Roseanne (Roseanne Barr) and Becky (Lecy Goranson) weren't so keen on letting him off the hook. Though supportive of David's vow to be a better father to his kids, both expressed their apprehension about David and Darlene suddenly jumping back into their relationship after two decades of not being able to make it work.

"You guys are a disaster as a couple," Roseanne told Darlene.

Given their many breaks ups over the years, she certainly had a point. Darlene realized this too and made the smart decision not to rekindle things with David after all, effectively closing the book on their long and tumultuous relationship. "You're gonna do what you came here to do," she told him at the end of the episode. "You're gonna be a great father."

Although this marked Galecki's only appearance this season, it looks like David might be sticking around for good this time.

But David wasn't the only Roseanne alum to make their way back to the series in the revealing episode. Roseanne and Jackie's (Laurie Metcalf) mom Bev (Estelle Parsons) showed up after being kicked out of her nursing home for enjoying a "healthy sex life." After infecting several other patients with gonorrhea, she was deemed a danger to others and forced to search for shelter elsewhere — namely Roseanne's home. Despite an already crowded house — Darlene moved back in with her kids after losing her job — Roseanne welcomed her mom with open arms.

Roseanne airs Tuesdays at 8/7c on ABC.

Sara Gilbert and Johnny Galecki, <em>Roseanne</em>Sara Gilbert and Johnny Galecki, Roseanne