The choice of simulations is out of Ariel's and Jenna's hands. Since taking over as NASTI's financial benefactor, Persephone and Hades have been thrusting them into simulations with increasing peril.

In this simulation, they find themselves on Moonbase Alpha. Something is amiss with the nuclear storge facility. Eagle pilots are returning with what looks like radiation burns, but no radioactivity is detected. No alarms have sounded, radiation sensors at the waste facility, five silos dug deep into lunar basalt, show safe levels of radiation. Ariel and Jenna are sent to investigate in person.

This is their harshest assignment yet: investigating Moonbase Alpha's nuclear waste facility, underground containment chambers containing hundreds of tons of volatile uranium-235 and plutonium-239 reclaimed from disarmed warheads, spent reactor fuel rods, and other hazardous radioactive waste.

They discover something is terribly wrong, and work to stave off a chain reaction that may lead to nuclear fission. Are they too late?