The team recovers a Roman plate that holds research on a synthetic gill unit tied to the research of a Professor Pendergast. Judson loses the plate when he and the curator are attacked while Gabe and Mac track the doctor to an insane asylum where he insists he is from Atlantis. Pendergast's partner Helmer needs the rebreather unit to silently get into a UN-quarantined area with sunken toxic gas tanks protected by sensors and is in league with the folks running the asylum to get the info out of Pendergast. Gabe and Mac try to break Pendergast out but Mac and Pendergast get captured and Helmer threats Mac to get Pendergast to give him the secret. Judson recovers the plate but figures out the curator is in on things. Gabe and Judson break them out and Judson confronts Helmer at the site and takes him out. Pendergast departs at the end, suggesting that he may not have been as insane as he appeared when he claimed he was from Atlantis...