Over the centuries, the thieves, assassins and secret agents who operate within the underworld have come up with many ingenious devices for stealing and murdering, many of which are disguised well enough to be carried in plain sight.
Actually a real-world fungus, just heard about it. A fungus that tastes well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick, pains, vomiting, all the fancy stuff. Was really used to cure alcoholism. May be a joke or to make sure the heroes spend their time focused on the mission.