Two prototype energy cells were stolen from the U.S. government by a double agent known as the Ice Man.  Jaime Sommers infiltrated the Princess Louise cruise ship to recover the stolen energy cells.  

The energy cells are approximately the size of a D Cell flashlight battery.  They are harmless when kept at cool temperatures.  However, if the cells are heated they will explode with the equivalent force of 1000 pounds of TNT.

Before exploding, the cells emit a faint hum audible to Jaime's bionic hearing.

(BW: Assault on the Princess)