At the end of a week we recognized that this switch business was a delusion and a snare.

We also discovered that a band of burglars had been lodging in the house the whole time--not exactly to steal, for there wasn't much left now, but to hide from the police, for they were hot pressed, and they shrewdly judged that the detectives would never think of a tribe of burglars taking sanctuary in a house notoriously protected by the most imposing and elaborate burglar alarm in America.
"Sent down for the expert again, and this time he struck a most dazzling idea--he fixed the thing so that opening the kitchen door would take off the alarm.

It was a noble idea, and he charged accordingly.

But you already foresee the result.

I switched on the alarm every night at bed-time, no longer trusting on Thomas's frail memory; and as soon as the lights were out the burglars walked in at the kitchen door, thus taking the alarm off without waiting for the cook to do it in the morning.