Things get even darker in new 'Avengers: Age of Ultron' trailer

Marvel has unleashed a new trailer for one of the most anticipated movies of spring 2015. The video reveals plenty of unseen footage, along with a few new plot details.

After the show-stopping battle depicted in the first film, released in 2012, Tony Stark (Robert Downey Jr.) sets out to establish a new planetary defense system to replace the S.H.I.E.L.D. But his plans are compromised by Ultron (James Spader), a psychopathic robot born of the experiments of a billionaire tinkerer and of the technology of the Chitauri -- aliens who previously attempted to invade Earth.

The Avengers must come together to take down Ultron and other enemy forces. But as the trailer shows, conflicts arise within the group, namely between Iron Man (Robert Downey Jr.), Thor (Chris Hemsworth), Captain America (Chris Evans) and especially the Hulk (Mark Ruffalo).

"Avengers: Age of Ultron" hits US theaters May 1, 2015.

Watch the trailer: youtu.be/MZoO8QVMxkk