Isumus is a science fiction action romance novel. It is the story of an outer civilisation that has built a source of free energy, and it explores the difference free energy could make to an economic structure.

Soldier Cassey Night meets Mark Stevens while on a reconnaissance mission on Earth. They fall in love, and she chooses to remain on Earth once her mission is complete.

Once Cassey defects, Major Helen King sends the Sethil, inhabitants of the second planet of the Korr-Sethil binary system, to Earth, a force she uses in secret as deniable muscle. Life hangs in the balance as Cassey and Mark fight for their future together on Earth.