In the Absence of Light — Sarah A. Hoyt

In this short story, Sarah A. Hoyt takes us to a time when space travel has many of the same sort of tales that sea travel did several centuries ago. So these monsters really exist or are they just the figments of overly active imaginations? The crew and passengers of the the Amadryad will all too soon learn the answer to what happened to those who'd traveled on the the Tenebras, the first colony ship to Tau Centauri as well as learning if the drifters are real or nothing more than tales meant to frighten people so they don't look too closely at what is really happening.