the gag that stops even the last expression

The murder weapon is an instrument of silence, the "best call-for-help-stifling gag in the world," and its work is total: it stops not just DuPlessis's pleas but his final human gesture. The one thought he has as he suffocates, the rueful recognition of how dumb a death this is, cannot even reach his own face, the grin denied by the towel and tape. Communication is sealed off all the way down to the smile a dying man would make, so that the interior goes fully dark with no way out.