The emotional 'Grey's Anatomy' scene where Addison meets Derek's kids for the first time is an act of 'ultimate forgiveness,' the episode's writer says

• Kate Walsh's character Addison Montgomery returned to "Grey's Anatomy" on season 18 episode three.
• Addison met ex-husband Derek Shepherd's kids at the end of the episode. Derek died in season 11.

Kate Walsh returned to "Grey's Anatomy" as Dr. Addison Montgomery on Thursday in an emotional episode titled "Hotter than Hell."

After Addison breaks down in an elevator with Meredith Grey (Ellen Pompeo) because she doesn't feel Derek's spirit in the halls of Grey-Sloan Memorial Hospital, Meredith reminds her late husband's ex-wife: "He is here. And he's in his children. And they are very real."

Meredith invites Addison to come and meet Zola, Bailey, and Ellis, and we get to see it happen on-screen in the episode's final scene. If you had dried your eyes and recovered from Addison's emotional moment in the elevator, this scene probably had you crying a new round of happier tears.

The episode's writer, Jamie Denbo, spoke to Insider about what it was like to pen these scenes and then watch them come to life.

Addison meeting her late ex's kids for the first time is a loaded moment for both her and Meredith

Denbo explained that meeting Meredith's children is an act of "ultimate forgiveness" between the two women who have so much complicated, and often negative, history between them.

As longtime "Grey's Anatomy" fans will recall, Meredith doesn't know that Derek is married when she gets involved with him on season one, but the affair does make the cracks in Derek and Addison's marriage deeper. Addison places blame directly on Meredith for the affair when she shakes her hand and says, "And you must be the woman who's been screwing my husband."

Season 18 is a long way from season one. So much time has passed, and with Derek dead now, Addison and Meredith's relationship is bound to transform. "The ultimate forgiveness, the most vulnerable you can be is to allow your children to be exposed to someone," Denbo told Insider. "You don't let your children connect with someone you don't trust, love, forgive, and to me, that's the ultimate kindness."

Denbo and Walsh know each other from their days in comedy together and the writer, who invited Walsh to her wedding to "The Big Bang Theory" actor John Ross Bowie, told Insider that she's happy that Addison's introduction to the Shepherd children allowed the world to see Walsh's improv skills.

"For those of you who haven't done deep dives on Kate Walsh, she's one of the funniest people on the planet," Denbo said. "And the entire ice cream at the table sequence when she's hanging out with the kids, is Kate hanging out with the kids, as Addison, she's not leaving her character." Denbo was on the "Grey's Anatomy" set for the filming of that scene and said it "was so touching and loving and funny" to watch it all unfold.

The episode's final scene is "the ultimate gesture on behalf of Meredith to say, 'We're good. The past is the past. We've loved, we've lost. Look at all we've been through,'" according to Denbo.

Plus, Walsh confirmed for Entertainment Tonight that Addison is still happily married to Jake ("Private Practice" star Benjamin Bratt) so she probably hasn't mused about what could've been with Derek for a long time. There is truly no bad blood for the interns to talk about anymore.

"Grey's Anatomy" airs Thursdays at 8 p.m. EST on ABC.