Maggie (Kelly McCreary) will soon discover the fling going on between Meredith (Ellen Pompeo) and Nathan (Martin Henderson). Meanwhile, there is no foreseeable ending for Shonda Rhimes' "Grey's Anatomy" according to ABC.

"Grey's Anatomy" season 13 returns with episode 21 this Thursday, titled "Don't Stop Me Now," where Maggie learns about the fling that's happening between Meredith and Nathan.

As seen from the episode 21 promo, while Nathan talks about how Meredith saved the day during their rocky flight, Maggie notices how he's rubbing her half-sister's shoulder and how she's responding to it happily.

In an interview with TVLine, McCreary shared that Maggie will be weighing her feelings for Nathan versus how Meredith has supported her when her mom passed away.

"Meredith and Maggie have gone through something so extreme together, and I think the whole Nathan question has been completely irrelevant this whole time. ... I think it becomes about weighing, 'Oh, there's this guy that I liked' against this life-and-death experience that they've shared," McCreary explained.

With that said, it seems that Maggie will be able to forgive Meredith for hiding her thing with Nathan sooner rather than later.

Meanwhile, "Grey's Anatomy" season 13 seems to have no end for ABC, Pompeo confirmed.

However, in an interview with Variety, the lead actress says that the show's life is really up to their fans.

"I'm really open to whatever the universe presents," Pompeo says, adding that she's not really sure how long the show will continue.

"I know the network and the studio like to say they see no end in sight, but I think the audience will tell us when the show is no-longer a fan favourite," Pompeo said. She went on to say that they're still very lucky that fans of "Grey's Anatomy" have stuck to them since the beginning.

"Grey's Anatomy" season 13 returns with episode 21 on Thursday, April 27, at 8 p.m. EDT on ABC.