While searching for the cause behind the sinking of several ships, Modo and Octavia sail to the exact coordinates of the attacks. Is it a sea monster? Or something else? They aren't alone in their pursuit: the beautiful and mysterious French agent Colette has been researching this phenomenon for some time. Upon reaching the site, Modo and Octavia's ship is rammed, and Modo is plunged into the icy sea... and disappears from sight. As he faces certain death, Modo is saved by a most unlikely underwater rescuer and discovers the mechanical truth behind the attacks. But the Clockwork Guild closes in. How will he get back to the surface?