Trama

Five friends are terrorized by a supernatural entity after downloading a mysterious app.

Having downloaded "Mr. Bedevil," a mysterious Siri-like A.I. app, a paranormal presence stalks teenager Nikki in her home. Nikki is found dead from shock inducing a heart attack.

Following Nikki's funeral, her boyfriend Cody, her best friend Alice Gorman, Alice's boyfriend Gavin, Haley Davis, and Haley's boyfriend Dan mysteriously receive invites to download "Mr. Bedevil" from Nikki's phone. After installing, each teen is taunted by Mr. Bedevil through their phones and becomes supernaturally haunted according to their personal fears. Gavin is tormented by clowns, Haley by a childhood teddy bear, and Dan by a grim woman from an old family photograph. Alice sees visions of her dead grandmother while Mr. Bedevil takes the form of a police officer and a white woman to frighten Cody. The friends also discover brands on their bodies in the shape of Mr. Bedevil's app icon.

The five friends eventually accept that the app has inexplicable abilities and intends to kill them. Mr. Bedevil uploads Haley and Dan's sex video to the internet. Gavin tries smashing his phone but it reforms. Dan tries making a police report but the attending officer ends up possessed by Mr. Bedevil.

Mr. Bedevil impersonates Alice and calls Gavin to come to Alice's house. There, multiple clowns torment and kill Gavin. Alice comes home and discovers Gavin's body.

Alice recovers Nikki's phone since that is where the invites came from and Cody hacks into it. Cody discovers that Nikki received her app invite from Samuel Price, Nikki's former physics tutor who was also a pseudoscience enthusiast.

Alice and Cody go to Sam's house and find his body under a bloody sheet in the garage. They also find audiotapes of Sam's research in which Sam identifies Mr. Bedevil as a paranormal presence who uses the app to enter reality in a manner similar to a Ouija board.

Haley is murdered by a killer teddy bear. Dan is killed by a vision of the woman from his family photo.

Cody finds a way to finish writing code started by Sam that will uninstall Mr. Bedevil from his and Alice's phones. Because the app is capable of adapting and rewriting its firmware, Cody can only use his program when Mr. Bedevil enters the physical world by first connecting to the phone's hardware.

Cody and Alice set a trap for Mr. Bedevil at a warehouse using two separate computer stations. Mr. Bedevil enters through Alice's phone and torments her in the form of Alice's grandmother. Cody's program successfully uninstalls the app from Alice's phone and Mr. Bedevil vanishes.

However, Mr. Bedevil then comes for Cody through Cody's phone. Alice attempts to banish Mr. Bedevil through the second computer station but the uninstall program freezes. Cody dies.

While attending college some time later, Alice Facetimes with her mother back at home. Alice is horrified to discover her mother is now using the Mr. Bedevil app herself.