While we anxiously await the Grey鈥檚 Anatomy鈥檚 firefighter spinoff , there鈥檚 still plenty of drama over on the original series. (Spoilers ahead for the September 28 and October 5 episodes.)

On the season 14 premiere two weeks ago, McDreamy鈥檚 neurosurgeon sister Amelia Shepherd was diagnosed with a brain tumor 鈥 something that the actress who plays her, Caterina Scorsone, was actually relieved to discover.

Any Grey鈥檚 fan will tell you that Dr. Shepherd鈥檚 behavior over the last couple of seasons has been鈥 well, unpredictable. She鈥檚 had issues in the past, of course 鈥 her drug addiction was a major story line on Private Practice 鈥 but recently she鈥檇 been especially erratic.

鈥淲hen I heard about the story line, my initial reaction was, 鈥楽o that鈥檚 why!'鈥 Scorsone told E! News . 鈥淏ecause it is definitely apparent that Amelia鈥檚 behavior has crossed over from a place of 鈥極h, she鈥檚 quirky and she does kind of wild, bold things鈥 to 鈥榃hat is she doing?鈥 in a kind of disturbing way.鈥

The actress went on to say that, looking back, something was definitely awry. 鈥淪he was making decisions that were just erratic and not consistent. They didn鈥檛 have any line of consistency. She鈥檇 say one thing and then she鈥檇 do another, and she鈥檇 leave because she was freaked out about one thing and get in a fight. It just seemed like it wasn鈥檛 respective of her personality鈥 something was off.鈥

Scorsone said she usually keeps herself in the dark about upcoming plot twists because she wants to 鈥渘ot know what [Amelia] doesn鈥檛 know.鈥 But she confessed to E! that she approached people behind the scenes about this situation. 鈥淲e kind of had a few conversations about it like, 鈥榃hy is she doing this.鈥 So, hearing that there was actually a physical, medical reason for some of the erratic behavior actually felt pretty good. It made a lot of my questions disappear.鈥

Shepherd will undergo surgery on tonight鈥檚 episode (Thursday, October 12), but that doesn鈥檛 mean that all of her troubles are over. In fact, things might be even worse as Amelia recovers. 鈥淚t鈥檚 not a walk in the park,鈥 Scorsone told E! News. 鈥淚 think she does not wake up immediately from the surgery, ready to go. When she wakes up, it鈥檚 pretty scary. It鈥檚 touch-and-go for a minute.鈥

We鈥檒l be able to see just how scary things get when Grey鈥檚 Anatomy airs Thursdays at 8pm on ABC.

Were you relieved to find out that there was a medical explanation for Dr. Amelia Shepherd鈥檚 erratic behavior? Let us know @BritandCo !

(Photo via ABC/Mitch Haaseth)