The oblique magic that has suffsed all his writings--from One More Spring and Portrait of Jenny to Mia--finds fresh expression in Robert Nathan's new novel, The Elixir. It has Merlin in it, and an airplane hijacking; King Richard the Lionhareted and Palestinian guerrillas; Blondel and the Old Man of the Mountain. And most important of all, a young English lady, first encountered playing the guitar at Stonehenge . . .