This is the second book in the Virus series, which parallels the SIMPOC series.
A suspicious virus has killed 99.99997 percent of the people. A ruthless warlord who moved into the White House attacked the government at Camp David. The president moved the remaining government to an aircraft carrier in the Atlantic and left a military unit to deal with the warlord.
The decimated US Navy is still functional. They must defend themselves from the remnants of militaries with a grudge against the US that use the opportunity to get revenge.
Joan Herl and her remaining space station Oasis crew returned to Earth, and a computer playing by different rules attacked them. Their only ally was the first thinking computer SIMPOC and his surrogate Alpha. Dr. Julius, who was one of the moon colony crew members, steals the research for thinking computers, and with his expertise he creates another computer that rivals SIMPOC and who starts making its own plans.
Eventually, they all find out why the virus started and who is responsible.