Never before in the history of his connection with the Hotel du Lac had Gustavo encountered such a munificent, companionable, expansive, entertaining, 'thoroughly' unique and inexplicable guest Even the fact that he was American scarcely accounted for everything. Yesterday this guest had rung the bell and demanded a partner to play lawn tennis - as if the hotel kept partners laid away in drawers like so many sheets. The guest, Jerymn Hilliard, Jr., is unexpectedly at loose ends in tiny Valedolmo. He has seen all the 'Baedeker' sights already... Then he learns that in a rose-colored villa, surrounded with cypress and with a 'terrazzo' on the lake, lives another American - one with a daughter: a Signorina Constantina: 'beautiful like the angels in Paradise,