The Village of Lost Children
"Men and women walk the streets of Stonefoot, but the laughter of playing children is nowhere to be heard. Over the past year, the village's children have gone missing in the middle of the night. Who will uncover the mystery of these disapearances and stop the curse before it leaves Stonefoot without a future?" From the DMsguild description.
The party is tasked with saving the last child in the village and eventually retrieving the kidnapped children. The villains first appear to be goblins, but after a hunt and a fun teleportation maze, they find out a human mage is behind it. The mage has been transmuting the children into human-goblin hybrids.