The second chapter in the Ultimate Galactus Trilogy, Ultimate Secret was begun by Warren Ellis and Steve McNiven, but McNiven's schedule caused him to drop out of the series after the second issue. Tom Raney replaced him, but the series still suffered a long delay before all four issues were finally published.

Ultimate Secret was very different in tone from the first series in the trilogy, Ultimate Nightmare. It adopted a more high action, superhero adventure story than Ultimate Nightmare's scifi horror story. It centered around the debut of the Ultimate version of Captain Marvel but also debut the Ultimate versions of Carol Danvers, Yon-Rogg and the Kree race in general.

The Ultimate Galactus Trilogy continued with Ultimate Extinction.

Plot Summary

Kree spy Mahr Vehl defects when the commander the expeditionary force he came with, Yahn Rgg, has gone mad due to Gah Lak Tus and decided the humans must not be allowed any chance to escape their fates. Mahr Vehl, patronizingly referred to as Captain Marvel, alerts Nick Fury, who calls in the Ultimates and Fantastic Four to face the Kree threat. Yahn Rgg's ship is destroyed, and Fury acquires their data on Gah Lak Tus in the hope of finding some way to defend Earth from the real threat.

Collected Editions

• Ultimate Secret: Ultimate Galactus
• Ultimate Galactus Trilogy

Non-U.S. Collected Editions

• Coleccionable Ultimate - Galactus 1: La Pesadilla (#1-2) (Spanish)
• Coleccionable Ultimate - Galactus 2: La Extinción (#3-4) (Spanish)
• Marvel Deluxe. Ultimate Galactus Trilogy (#1-4) (Spanish)

Translated into Spanish.