The spooky season mercenaries were caught on musician Cody Tate's ring camera after he put out a generous helping of candy for trick-or-treaters ... so he could settle in at home, undisturbed, to watch the World Series.

However, an unidentified woman paid little attention to his sign clearly instructing people to take just ONE piece of candy.

You can see in the video she races to the bowl with a group of kids ... and they all frantically grab handfuls of sweet treats and shove them in their bags.

Seemingly oblivious to the camera, the smirking woman in a gray hoodie -- potentially the kids' mother -- ensures everyone's bags are full to the brim, takes one last look at the bowl and then leads her fleeing crew.

Cody, who plays guitar in the southern rock band Whiskey Myers, was pretty devastated and posted the vid and said "this is why you can't trust people" -- and added he was particularly shocked to see adults behaving like this.

He wants justice, though, and asked his followers to repost the video, and try to identify the perpetrators, who, he pointed out, ruined Halloween for all the other kids who hadn't come by yet for candy.

Luckily, it wasn't a lost cause as one of Cody's kind-hearted neighbors saw the candy grabbing caper in real time, and came over to restock the bowl with candy.