Thanks to collider.com we have a nice little description from the Avengers Infinity War Trailer that was shown today at Disney's D23 Expo. 

The footage began with the Guardians. “We are arriving,’ says Mantis as the Milano pulls into an uncertain territory. Quill pipes up, “Don’t forget this might be dangerous, so let’s put on our mean faces.” Suddenly a body slams into the front of the ship. It’s Thor! His face is all smushed against the glass (nice callback to doctor’s office in the the original film). The Guardians haul his unconscious body inside, lay him out on a table, and Mantis wakes him up. Thor comes out of it swinging, and the Guardians point their weapons. He looks around confused and asks what’s going on.

The scene transitions to Scarlet Witch, dodging an energy blast that slams into the truck behind her, cleaving it in half. Loki stands among ruins, holding the Tesseract cube. Riding on a school bus, Peter’s Spidey Senses (confirmed!) kick in, standing up the hairs on his arm. Iron Man is with the Guardians, gearing up for battle. “We have one advantage,” he says. “He’s coming to us.”

Thanos’ voice booms in. “Fun isn’t something one considers when balancing the universe, but this does put a smile on my face. Gamora is standing amongst wreckage, looking terrified, tears in her eyes. From here the shots get quick. A spacecraft crashes to the ground. Thanos warps into frame, walking through a portal. Doctor Strange is casting magic. Star-Lord is battling Thanos. That sick suit we saw at the end of Spider-Man: Homecoming? Spider-Man flies into scene wearing it, a glinting metallic update of the classic suit. Bucky and Black Panther are leading armies.

Cap steps into frame, with a BEARD and looking like he’s seen some shit. Hulk Buster makes an appearance. Vision looks stressed and maybe like he’s stuck in a cage? Could just be framing though since Vis ain’t too fond of walls. Thanos grabs Thor by the top of the head, crushing his skull. Black Widow has bleach blonde hair. Thanos punches Iron Man right in the face, sending him flying. Wielding a partially assembled Infinity Gauntlet, Thanos reaches towards the sky and pulls down a moon, sending the fractured comets flying at our heroes. In rolls the title card, and scene.

It looks dark and dramatic, and utterly epic. It’s clear Marvel is trying to do something different here, not just through the visual cues like Cap’s beard and Natasha’s hair, but to pay off a decade’s worth of narrative and world-building. While it’s impossible to tell from two minutes work of footage, it certainly looks like that gamble paid off.

Avengers: Infinity War arrives in theaters May 4, 2018