Orpheus Lost by Janette Turner Hospital

Belonging to the genre of family and relationships, the main character Leela, a maths genius, meets an Australian musician Mishka, while he is busking in the subway.  They soon become lovers.  There is an explosion in the underground and terrorists are suspected.  An investigator, Cobb who is a childhood friend of Leela's, suggests Mishka may not be all he seems.  He appears to have spent quite a bit of time a a cafe known to be a terrorist meeting place and contact point. His kidnapping brings all suspicions to a head with an unexpected outcome.