Gentian Hill by Elizabeth Goudge
Unable to bear the prospect of a life at sea, young Anthony O'Connell deserts his ship at Torquay and escapes into the Devonshire countryside under a new name. When Stella Sprigg, adopted daughter of a local farmer, encounters 'Zachary', the pair instantly know they are destined to be together.
Intertwined with the local legend of St. Michael's Chapel, Stella and Zachary's story takes them from the secluded Devonshire valley to the perilous Mediterranean seas and finally to the poverty and squalor of eighteenth-century London.