Black harvest - Ann Pilling

The rugged west coast of Ireland seems like the perfect place for a holiday. Then everything starts to go wrong. Colin is aware of an awful smell coming off the land, a smell of death and decay

Colin and Prill were looking forward to a holiday of fun and adventure in Ireland. It would have been perfect if only they hadn't had to drag along their "odd" cousin Oliver. But Oliver, it turns out, isn't their biggest problem.
Almost from the moment they arrive, Colin feels sick from an awful smell, so powerful and horrible that it seems to be rising from the land of the dead. At the same time, Prill is visited by a strange creature creeping into her dreams. Who is she, and what does she want?
Only Oliver seems untouched by the danger. As the hot summer days continue, their terror mounts and their baby sister becomes critically ill. Oliver links the present horror with the terrible famine in Ireland of the 1840s - and the strange occupant of the nearby caravan, whose land was lost then through eviction - and he must bring about the reconciliation to save himself and his cousins.