Lionsgate has released the second trailer for their upcoming action-comedy American Ultra, arriving in theaters August 21. The trailer actually expands upon a new movie clip that was released last week, which took place after the seemingly-hapless stoner Mike (Jesse Eisenberg) killed two men. We get to see what actually happens that leads up to this killing, and how Mike gets 'activated' as a sleeper agent.

The trailer sets up the premise that the government has been conducting secret experiments to create "super soldiers," with a number of sleeper agents living among us in plain sight, unaware of their actual abilities. We then see Mike working at a convenience store when a mysterious woman (Connie Britton) says a few key phrases that activate this agent, leading to him killing two men who are "doing stuff" to his car. Kristen Stewart also stars as Mike's girlfriend Phoebe, who gets caught in the middle of all the action.

We also get a glimpse at Topher Grace as Adrian Yates, who appears to be a government agent who is trying to corral Mike, and John Leguizamo as a colorful character named Rose, who clearly doesn't want to get in the middle of Mike's sorted affairs. The supporting cast is rounded out by Walton Goggins, Bill Pullman, Tony Hale, Lavell Crawford and Monique Ganderton. It's quite clear from this new footage that we won't see an action movie quite as unique as American Ultra as the summer movie season winds down.

Related: American Ultra Brings Free Weed to Comic-Con

American Ultra had an unusual presence at Comic-Con a few weeks ago, giving out free weed and debuting new posters for the San Diego crowd. It remains to be seen if this unique campaign will create a bigger audience for the movie, which hits theaters August 21. American Ultra will go up against Sinister 2 and Hitman: Agent 47 in wide release next month. It's possible that this original movie with a marketable cast can outshine the horror sequel and action reboot, to bring the summer movie season to a close on a high note, but we'll have to wait and see.

Nima Nourizadeh follows up her directorial debut Project X with American Ultra, which was written by Max Landis (Chronicle). Can American Ultra elevate the "stoner" genre to new heights with its inventive story and action scenes? Check out the latest trailer and chime in with your thoughts.