Tom shrugged. "An optimistic guess is that they spotted our Navy search force and pulled out quickly, fearing a surprise attack."
"What's a pessimistic explanation?" Bud asked.
"Mission completed," Tom said grimly. "No need for them to stick around if they'd already snagged the missile."
Bud scowled at the thought. "Oh, no! That mustn't be true!"
Tom plopped down at his desk, frowning. "Bud, I've been itching to get to work on a non-detectable sub, like the one that attacked us. But maybe it would be smarter to get a line on Mirov's pals first."
"You mean down in the South Atlantic?"
Tom nodded. "I'd sure like to know if they found that missile."
"You and I both, pal!" Bud agreed. "Hey! We could use the electronic hydrolungs for scouting around!" he added eagerly.
"I intend to," Tom said. "But we'll need speed to cover the area. So first I want to add an ion drive to our equipment."
"Ion drive? For underwater?" Bud, who was familiar with ion propulsion for spaceships, wrinkled his brow in a puzzled frown.