"Grey's Anatomy" season 13 will shed light on what Jo (Camilla Luddington) has been keeping from Alex (Justin Chambers) all these years.

In the previous season, it was revealed that Jo could not marry Alex because she has a husband, and an abusive one at that who threatens to hurt her if she files for divorce. What's worse is that Jo has been living under a false identity.

In "Grey's Anatomy" season 13, more details about the Jo bombshell will be revealed. It is unclear as to when Alex will find out and how he will react, but it looks like the mystery will last a whole season.

"It's very explosive, very exciting and interesting on social levels and personal character levels," Caterina Scorsone, who plays Amelia, revealed during the Television Critics Association press tour.

Speaking of Amelia, she and her husband Owen (Kevin McKidd) won't get a lot of screen time in the "Grey's Anatomy" season 13 premiere so it is expected that the Jo-Alex storyline will be the center of the season opener.

A few months back, Luddington said that her character will now be compelled to confront in "Grey's Anatomy" season 13 the very problem she worked so hard to avoid, something that Jo is frightened to even think about.

"She now has so much to explain, not just why she's been married, or why she didn't tell him, or that it's not her real name," the actress told Entertainment Weekly.

"Now she has to also explain how she got herself in a situation where it looks like cheating, and that she wasn't cheating. I wonder if it's just all too much to recover from," she went on to say.

Alex has attempted to propose to Jo previously, but she rejected him. The same happened in the previous season, although this time, he wanted an explanation, which, in the end, he did not get.

It is unknown how Alex will respond when he learns the truth, but it looks like it will be a mystery until "Grey's Anatomy" season 13 wraps up.

"Grey's Anatomy" season 13 premieres Thursday, Sept. 22 at 8 p.m. ET on ABC.