Veronica Stallwood: Oxford Shift [2000] paperback

Joyce Fielding walked out one afternoon into the streets of Oxford and just disappeared. And now, Kate Ivory has been hired to find her. Joyce is a respectable widow in her sixties and there is nothing at first glance to explain her disappearance, so Kate consults her own mother, the irrepressible Roz, to help solve the puzzle. It isn't long before Kate, following Joyce's trail, discovers a dead body. The police may think that Joyce is a murderer and Kate an interfering amateur, but Kate realises that Joyce has unwittingly walked into danger, and that the hunt for the missing grandmother is a race against time...