There is a lot of detail the characters won't encounter. There are opportunities to weave the main plot and subplots together, but they don't have to be. The patron's write-up details his long term actions in either event. The characters can either sign on with this patron or remain acquaintances with a mutual enemy. In fighting the big bad, the characters will inadvertently befriend a powerful patron who is fighting the big bad for his own reasons. The motivation behind the main plot is vested in the organization and the story will go on with someone filling the big bad's boots.
But should the characters manage to kill the big bad before the main plot is resolved, he has an organization and lieutenants. The big bad is not chasing the characters directly. If the players miss an encounter, the motivation for that encounter remains unsatisfied, and the NPC involved remains to try again a different way.
For example, the characters must upgrade their ship at one point to continue the quest, but what players don't want to trick out their ride? The bulk of the plot is driven by the motivations of various NPCs. There are a few encounters the characters must go through, but these are rare and not obnoxious. The end goal does not require the characters to head straight for it with no variation. Each step concludes with a sense of accomplishment before the next step is revealed. There are clear intermediate steps to the end goal. This goal acquires some additional details as play progresses, but the core is there in session one. The end goal is presented in the first session, get Object A to Point B and into the hands of Person C. Click to expand.It's very well designed and written.