Fugue in a Minor Key. Operation Quickline, #4

After a hard afternoon waiting in the rain for a contact that doesn't show, all spy and freelance writer Lisa Wycherly wants to do is go home and read a book by the fireplace. But family matters intervene. Lisa's nephew Darby is having trouble at school. Lisa's boss and housemate Sid Hackbirn agrees to let Darby come stay with him and Lisa, not realizing that his own life is about to be turned upside-down.
An old friend comes by the house with a boy about Darby's age who looks remarkably like Sid. Rachel never told Sid that she was pregnant, but now it's time for Nick to know where he came from. Lisa suddenly finds her hands full trying to get Sid to acknowledge Nick, figure out what Darby's problem is and working undercover to set up a sting on a group of defense plant employees who are selling secrets.
It's a case that gets messier by the minute, with British intelligence sticking their noses in for an unknown reason and the likelihood that there's a leak connected to Sid and Lisa's FBI supervisor Henry James. As usual, it's hard for Lisa to say whether the greater danger is to her heart or to her life.