In Plain Sight

Plot: A string of disappearances has the local constabulary of Grand Coryan in a furor. A minor nobleman, a page of the Senate, and a bouncer at a local tavern are all among the missing. Suspicion falls upon a cowled figure who stalks the streets around midnight.

The truth: The Heroes find a Ymandragoran thrall alone in the sewers of Grand Coryan, a triggered trap, attuned to hunting down arcane magical resonances. Placed there by a Harvester to capture unwary casters, the thing emerges from the sewers only long enough to paralyze and drag a its victim back down, where it waits for the Harvester to check his trap for his prize.

Notes
–The thrall is a bioconstruct, as all thralls are, and this one looks completely human. It captures its victims any time of the day, as it can move unnoticed through crowds. It only has a limited range, so it captures only Arcanely gifted people who use their magic in one particular town square.
–When the heroes find their way down to the sewers, the timing should be such that they meet up with the Harvester and his bodyguards who were checking on what his trap had caught.
–The cowled figure is a red herring: The brother/sister of one of the missing who has taken it into their head to track down and rescue/avenge their sibling. They will be wary of the Heroes, suspecting them of being in on the plot.