The master will return unannounced and unexpected. Matthew 24:50

“Watch therefore, for ye know not what hour your Lord will come; but you know quite well that the day of the Lord’s return will come unexpectedly, like a thief in the night. Be on your guard, so that your hearts will not be weighed down with dissipation, and drunkenness, and the worries of life, and that this day will not come upon you suddenly, like a trap. You also must be ready all the time, for the Son of Man will come when least expected.”