Crime on the Fens (DI Nikki Galena, #1)

The town is being terrorised by gangs of violent thugs, all wearing identical hideous masks. Then a talented young female student goes missing on the marsh and Nikki and Joseph find themselves joining forces with a master criminal in their efforts to save her. They need to look behind the masks, but when they do, they find something more sinister and deadly than they ever expected . . .