Next Of Kin — Ann Somerville

In a sequel to 'Every Move You Make', Nick and Anton have settled happily into married life. But on the eve of their 3rd anniversary, Nick disappears, apparently leaving Anton for another man. Anton refuses to believe it. His search for the truth takes him half way around the world, while Nick's friends work to discover what really happened to Anton's husband.

This novella is the third story in the 'Unnatural Selection' series.