AllMovie

The Blue Envelope Mystery was produced, appropriately enough, by Blue Ribbon Productions, a division of Vitagraph. The story is told in flashback from the point of view of heroine Leslie Brennan (Lillian Walker). Born into wealth, Leslie is ardently pursued by several fortune-hunters until word gets out that her father has gone broke. None the worse for her reversal of fortune, she goes to work as secretary for misogynistic young inventor Ewen Kennedy (John D. Bennett. While delivering the plans for Kennedy's latest creation, Leslie is waylaid and kidnapped by foreign spies. But she manages to outwit the villains by hiding the plans in her flowered hat, and in so doing wins the love of the formerly truculent Kennedy. Looking back on the whole affair, Leslie dismisses the danger involved, preferring to concentrate on the happy denouement.