Final answer:
Agatha was caught eating candy from Hansel's Haven when Hansel noticed the chocolate smudges on her face and the trail of chocolate leading from his candy jar to her hiding spot.
Step-by-step explanation:
Agatha's sticky fingers were discovered through a combination of circumstantial evidence and Agatha's own carelessness. The candy jar in Hansel's Haven was mysteriously empty, with only a few crumbs remaining. Agatha had been seen lurking around Hansel's Haven on several occasions. Agatha had a history of pilfering sweets from other children.
Agatha left behind a trail of chocolate smudges leading from Hansel's Haven to her hiding spot. Agatha forgot to wipe away a smear of chocolate from her cheek. Agatha couldn't resist bragging about her candy heist to her friends.
When confronted with the evidence, Agatha initially denied any wrongdoing. However, when Hansel points out the chocolate smudges and the smear on her cheek, Agatha is forced to confess.
Agatha's punishment for her candy-stealing crime was to apologize to Hansel and help him restock his candy jar. She also had to promise never to take candy without permission again.