The picture changed to the logo of the Threetown Public Library. Booker’s pleasantly monotonous voice came on. “Greetings, 1984. You may interrupt this message at any time by saying ‘We surrender.’ Please carefully watch the following coordinates (numbers).

“You have come to Threeworld to defend the USNE’s interest. That interest is based on our only export, Helium-3 or 3He. Your prompt surrender will preserve a large amount of 3He for you to continue to enjoy. To help you decide, we will now destroy the 3He reserves in three stages at 5-minute intervals. Stage 1, 1%. Stage 2, 10%. And Stage 3, the remainder.

“Helium in space exists as an inert, invisible gas. What we call ‘regolith’ is just common gravel in which the gas is entrapped. Free helium always escapes. This is why we drive tunnels underneath the regolith to mine the gas. Agitating the regolith, as with explosives, releases it. Any library cardholder may ask for details.

“Now commencing Stage 1.”

The ground shook from a huge explosion.