This Hitman 3 game guide video shows how to obtain 2 important quest items in the Thornbridge Manor in Dartmoor, England. Both the master key and the lethal posion can be found in Mr. Fernsby’s Office on the ground level. You can use a key or a lockpick or follow the route from our video to get the crowbar. The master key unlocks all other doors in the mansion and the lethal poison can be used to kill Alexa Carlisle.
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Additional info – Our video assumes you don't have any gadgets / items in your inventory. You can use a lockpick to access the office faster. You can also eliminate Mr. Fernsby and take his key.