Originally Posted by ArmouredHedgehog
It is a giant plot hole. But there are so many more. The intro does show the mindflayers picking people at random as hosts yet the random selection leads to a group of survivors as follows:

A vampire spawn
A wizard with explosive shadow magic inside of him
A warlock in pact with a Devil
A shar cleric on a secret mission to steal what likely is an infernal contract
A githyanki

They were capturing people in faerun, not in the wheel


There's also plenty of evidence that they've been capturing and implanting tadpoles for longer than this single raid. The three leaders of the Goblin camp are all infected as well, and they were on the ground to watch the Nautiloid crash and had already established themselves. Not to mention the whole 'Absolute' religion that's tied up in the whole mess has also had at least some time to get up and running. So not all the party members might have been gathered in the same run.