I'm playing the The Shadow Vault scenario. One of my heroes is carrying the objective token.

Can the Overlord use Dark Charm to force my hero to give the objective token to Baron Zachareth?

I'm playing the The Shadow Vault scenario. One of my heroes is carrying the objective token.

Can the Overlord use Dark Charm to force my hero to give the objective token to Baron Zachareth?

No, the text on the Dark Charm its very specific : "If he fails, you may perform a move or attack action with that hero as if he were one of your monsters this turn"

Remember also that Dark Charm gives you an opportunity to make the hero attack himself, which is not common. If you can make him KO himself, he'll drop the token (if I am remembering that quest correctly). He does get to roll defense, but since you're attacking you get to spend surges. Good luck!

Also note that it's a move or an attack, not use an action, a skill or ability or feat that includes a move or an attack.

Dark Charm is a very nice OL card, but it does have it's limits.

However, the rules say that a hero can hand his items to another hero as part of a move action. Doesn't that count?

However, the rules say that a hero can hand his items to another hero as part of a move action. Doesn't that count?

It does not. A hero can hand one item to another during a move action, but it isn't part of the action- it's a separate thing the hero gets to do during a specific time. A move action is nothing more than getting equivalent movement points to your speed and spending them.