In the 26th Century, humanity and the Covenant have a fragile peace after a long war. The Covenant secretly attacks Earth's colonies, and the ONI must stop them. On Planet Sedra, Commander Locke's team tries to stop a Covenant warrior, but the alien explodes a bomb in a mall, killing many. The team discovers the attack was biological, and the element is from Alpha Halo, where the sun is scorching hot. They head to Halo in the Condor, but are trapped by technology-attracting worms and must escape before the sun rises in five hours.

Halo: Nightfall
A team of investigators, led by Jameson Locke, is caught off guard on the distant planet of Sedra while probing terrorist activity, revealing a catastrophic biological assault that exposes a malevolent scheme.