The Children of Hamlin (Star Trek: The Next Generation #3) by Carmen Carter

The Hamlin Massacre – every Starfleet officer knows the tale. The tiny Federation outpost of Hamlin was destroyed, its entire adult population ruthlessly slaughtered, before the first defense shields could be raised. Even worse, the colony's children disappeared without a trace, abducted by the aliens who attacked with a ferocity and speed that outmatched their Starfleet pursuers.

Now, fifty years later, the Choraii ships have appeared again. But this time the Federation is ready; this time the Choraii must pay for what they need. The precious metals can only be bought with the Hamlin children still living with their captors.