Future/Perfect: Part 4 details the "Offsite" location, which can be reached from the facility found at the end of Future/Perfect: Part 3, and describes events that occur at an outpost in the distant past. Part 4 also introduces some additional elements that may be used throughout parts 1-3 if desired.
from the introduction:
It is highly recommended that Part 4 not be used as the introduction to this campaign.
The depth and complexity (as well as the remote location — in time and space) make Part 4 ideal as the culmination of the campaign and it is those same qualities that make it difficult if not impossible to imagine as a beginning. Parts 1, 2, or 3 should be used to ease the players into the subtleties and convolutions of the mission before Part 4 is even attempted.
However, adding elements from Part 4 (the Motion, the Great Race Agent) throughout other Parts of the campaign to expand and expound upon the mysteries presented here will help to reinforce the impact of Part 4 if and when it does arrive.