Safe Habour by Marita Conlon-McKenna

Sophie and Hugh are left homeless when their house is bombed during the London Blitz. Their mother is seriously injured and their Dad is away fighting, so the children are sent to their grandfather in Ireland. Sophie is scared - they have never met grandfather but his letters cause such trouble in the house, and their Dad never speaks of him.

How will they live in a strange country, with a man who probably hates them - and will the family ever be together again?