By Natalie Abrams
Updated February 18, 2016 at 12:00 PM EST
Credit: ABC

Warning: This story contains major spoilers from Thursday’s episode of Grey’s Anatomy. Read at your own risk!

Now we finally know the tragic story that led to Owen and Riggs’ falling out.

During Thursday’s episode of Grey’s Anatomy, Owen (Kevin McKidd) was finally forced to confront his past, revealing to Amelia (Caterina Scorsone) that his younger sister Megan died. Though it’s unclear how it happened, Owen places the blame on Riggs.

It turns out, Owen’s younger sister was brilliant; the siblings went to medical school together, which is where they met Riggs (Martin Henderson), who became Owen’s best friend. Megan fell in love with him before her demise. “He was with her the day that we lost her,” Owen told Amelia. “I trusted him and he was like a brother to me. He should’ve… but he didn’t.”

However, Amelia is quick to point out that Megan loved Riggs for a reason, so that makes him family — just like Derek (Patrick Dempsey) loved Meredith (Ellen Pompeo), which makes her family to Amelia. Whether that sage advice spurs Owen into letting Riggs back in his orbit, however, remains to be seen.

“They both have very different perspectives of what the actual circumstances were,” Henderson previously told EW of the then-mysterious event with Owen’s sister. As for how she died, Henderson has heard plenty of theories: “Some people were saying that I killed the sister,” he says. “Some people say I was operating on her and she died.” Share your theories below.

Grey’s Anatomy airs Thursdays at 8 p.m. ET on ABC.

Episode Recaps

Grey's Anatomy

Meredith. Alex. Bailey. The doctors are definitely in on Shonda Rhimes' hospital melodrama.

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