The Ultimates are unprepared for a quintet of mysterious visitors who appear in the midst of the team's top-security base of operations, claiming to be emissaries from the future. These "Tomorrow Men" say Earth's civilization is at a crossroads - on the verge of enslavement by a secret, immensely efficient organization known in the future as Tiber. Only the Ultimates have the skills and the firepower to ferret Tiber out of its nests around the world and crush its plans for global conquest. But wealthy Tony Stark, aka Iron Man, is dying by degrees of an incurable medical condition. For him, the temptation to make a change in the timeline may be too great to ignore - though mankind's future might be damaged in the process.