The Tigerfish makes its way under the ice to Zebra’s last known position. Ferraday decides to use a torpedo to blast an opening in the thick ice. However, the torpedo tube is open at both ends and seawater floods in, plunging the sub toward its rated crush depth. Ferraday and his crew are barely able to save themselves. During the investigation of the torpedo tube, Jones quickly determines that this malfunction should be impossible and, being an expert in sabotage operations, Jones even describes how someone could intentionally rig the tube to malfunction. Both Jones and Ferraday conclude that there is a saboteur aboard, and both suspect Anders, who is the one member of the rescue team who is the least known to Jones, Ferraday, and Vaslov. However, the mission is too important to abort.

Finally locating an area of thin ice, the sub surfaces. Ferraday, Vaslov, Jones, and a rescue party set out for the weather station. They reach Zebra to find buildings burned down and the scientists nearly dead from exposure. Jones and Vaslov begin questioning the survivors. It becomes obvious that the two spies are looking for something.