Blake Lively just broke her Instagram silence after sending her fans into a frenzy yesterday. Without warning, Blake unfollowed everyone and deleted all of her photos, including her profile picture. She also changed her bio to "What happened to Emily?" and randomly started following 37 girls named Emily Nelson.

After dropping a few clues on Twitter, Blake finally gave us an answer. She shared the first trailer for her upcoming movie A Simple Favor, and it's so chilling that it gave us goosebumps. 

@asimplefavorembedded via  

In the film, Blake Lively stars as Emily Nelson, a young woman who seems perfect on the outside, but her dark side is revealed when she suddenly goes missing. Her co-star Anna Kendrick plays her best friend, and goes on a mission to find out the mystery behind her best friend's disappearance.

In the trailer, Blake is as stunning and sophisticated as ever. There's a flash of her making out with Henry Golding, who plays her husband. Then it goes dark. All you can hear is Anna Kendrick's voice saying, "Everybody has a dark side, some of us are better at hiding it than others." Creeeeepy.

"Five days ago, Emily went missing," Kendrick says in the trailer, "I'm realizing I don't know her as well as I thought I did." Overall, the film looks like the perfect combination of mystery, suspense, action and enviable outfits.

A Simple Favor  doesn't hit theatres until September, but we're pretty sure Blake will keep the excitement going with new teasers on Instagram. 

Also did you know that the movie was filmed in a tiny town just outside of Toronto? Click here to find out where Blake and Anna were seen hanging out.