A fleeting moment can become an eternity. From a past encounter everything may disappear in the dungeon of forgetfulness. A few furtive flashes or innocent twinkles can survive, though. Some immateria...
He started keeping a journal - had been, in fact, secretly doing so for some time: the furtive act of a deranged person.
(a.) Stolen; obtained or characterized by stealth; sly; secret; stealthy; as, a furtive look.