Last week, "Grey's Anatomy" left the fans with a huge cliffhanger --- Amelia and Owen were waiting for his sister, Megan to be transported to the hospital after being missing for nearly a decade. Here's everything we know about one of the most mysterious characters on the ABC drama series.

Why Owen and Riggs dislike each other

Since Riggs arrived at Grey-Sloan, there has been a noticeable tension between them. A few months ago, the show mentioned that their differences could be traced back to Megan and the events that led up to her disappearance.

According to Closer Weekly, Owen blamed Nathan for his sister being in the helicopter.

Apparently, the chopper went through unprotected airspace ten years ago. The events that transpired the day she disappeared are a little fuzzy since Riggs and Owen had very different versions.

How Riggs and Megan met

Nathan, Megan, and Owen went to medical school together and became fast friends. After they had graduated medical school, they joined the military together. Megan and Riggs hit it off and became an item.

One day, they were working together and a patient needed to be transported on a chopper. There was only one seat available, and Megan said she would accompany her patient. Nathan claimed that he tried to talk her out of it, but she refused to back down.

"Grey's Anatomy" spoilers tease that when Megan didn't come back, Owen and Nathan began to worry.

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They searched for her for a long time. Eventually, Owen asked Riggs to stop looking for her and believed her to be dead.

Owen's side of the story

If you ask Owen about the events that happened on the day his sister disappeared, his take is much different than Nathan's. Owen suggested that Riggs was cheating on his sister and that is why she wanted to go on the helicopter. Then, Owen said that when the chopper took off, Nathan was nowhere to be found.

Apparently, Owen stated that Nathan's story about trying to convince Megan not to get on the helicopter was bogus. He never even talked to her because she was nowhere to be found.

Riggs' side

"Grey's Anatomy" spoilers revealed that Nathan admitted that he cheated on Megan. However, it came out that Owen knew about the affair, and he ordered his sister to go on the helicopter to get away from Riggs.

We can assume that Megan will face off against her brother and Nathan in Season 14. "Grey's Anatomy" hasn't revealed who will portray Megan yet. In the flashback scenes, Bridget Regan played Megan, so it's possible that she could return to the role.

"Grey's Anatomy" fans have so many questions about how Megan's return will impact Amelia and Owen and Nathan and Meredith.