sentry

This side of your chamber looks out upon a kind of open gallery, where patrols are continually passing, and sentries keep watch day and night.”

“And will you engage not to do any harm to the sentry, except as a last resort?”

In this passage he proposed to drive a level as they do in mines; this level would bring the two prisoners immediately beneath the gallery where the sentry kept watch; once there, a large excavation would be made, and one of the flag-stones with which the gallery was paved be so completely loosened that at the desired moment it would give way beneath the feet of the soldier, who, stunned by his fall, would be immediately bound and gagged by Dantès before he had power to offer any resistance.

Compelled, as they were, to await a night sufficiently dark to favor their flight, they were obliged to defer their final attempt till that auspicious moment should arrive; their greatest dread now was lest the stone through which the sentry was doomed to fall should give way before its right time, and this they had in some measure provided against by propping it up with a small beam which they had discovered in the walls through which they had worked their way.