Set against a colourful backdrop of modern gypsy culture, there\'s plenty of potential for a riveting mystery in The Invisible Ones, Stef Penney\'s second novel. Rose Janko has been missing for seven years. She was briefly married into the reclusive Janko family of gypsies before running off - according to them - with a \"gorjio\" (non-Romany). Private detective Ray Lovell is hired to find out what happened to her (Did she really disappear of her own accord or was she murdered?). Before leaving the Janko clan, Lovell is told that Rose gave birth to a son who suffers from the family curse, a debilitating illness that has plagued the family\'s males for generations. It\'s nothing that couldn\'t be identified with a few blood tests, but then there\'d be no book. Lovell tries to piece together a picture of what Rose was like as a person but no-one\'s talking, leaving the reader with the task of sustaining an interest in her anyway, over 300-plus pages. The plodding pace hinders any suspense, as clues are drip-fed. A dutiful twist adds intrigue but it\'s too little, too late.