The Zombie head is what remains of the Barrelchest Mk II after it is defeated during A Clockwork Syringe. The player has to interrogate it to determine who sent it and why. This is done by performing various forms of mild torture on the zombie in order to increase its stress levels. These include Wet willy, nose pinch, pig nose, shake head and insult. If the interrogation is started then left the player says "I'll be back to finish the job later."
When the head's stress levels reach maximum, it will explain that he was sent by Rabid Jack to destroy the player and that an army of more barrelchests are currently being built to launch a destructive wave on Mos Le'Harmless.
When the zombie head refuses to reveal any more information, the player picks up the head and puts it in their backpack to take the head to Bill Teach and inform him of the turn of events. In order to find out where the zombie head came from, Bill requests the player obtain the Twiblick night special, a set of feminine wigs and makeup, to be used on the zombie head. After being beautified, the zombie head tells the coordinates of Bloodsplatter Isle.