While making merry at the York Christmas Book Fair, Kitt Hartley finds herself drawn into a murder mystery with a festive twist. The victim is Leonard Bell, a festival volunteer who suddenly drops dead during his performance of A Christmas Carol.

The next day, police identify the cause of death as an unknown toxin. Fearing for his own life, Bell’s lab partner Kevin Ripley enlists Kitt’s help to track down the killer – before it’s too late.

As Kitt and her team begin to investigate the poisoning, they uncover a twisting web of long-held grudges and stolen antidotes. But even with surprise help from some very old friends, can Kitt unravel the truth? Or will the invisible assassin escape unpunished?