As he spoke, the young woman was fishing another "detector" from her purse. It was a limp bit of something which she placed to her lips and inflated until it was a foot-and-a-half in diameter, then she tied off the neck and proceeded down the walk waving it before her in great vertical sweeps.
It was as simple as that.
Our undoing had been an 85-cent kid's toy. And our salvation was a penny-balloon!