I tell you, on that day when the Son of Man will be revealed, there will be two people in one bed; one will be taken, the other left. After addressing the concern of the Pharisees (who wanted to know when the kingdom of God will come), Jesus turns to his disciples to remind them of the need to be vigilant. In the Gospel according to Matthew, Jesus concludes this passage by telling them to be awake so as not to be caught unawares at the coming of the master (cf. Matthew 24:42-44). To ensure that his warning hits home, Jesus uses a few examples that he knew the disciples would be familiar with: the great flood at the time of Noah and the misfortunes that befell Sodom and Gomorrah. In both examples, people ignored the warnings they were given and refused to utilize the ‘grace’ period they were given. It did not end well for those who refused to hearken to the warnings. 
The coming of the Son of Man will both be a surprise and not a surprise at the same time. While no one will know the exact time and day (cf. Mark 13:32), there will be a ‘general’ knowledge about it ( where the body is, there the vultures will be). During the days of the great flood, men and women were busy living their lives until they forgot to notice Noah building the ark. Had they paused even for a minute from their revelry, curiosity might have prompted them to inquire from Noah what was going on. Had this happened, perhaps they might have escaped the floods. In like manner, the coming of the Son of Man will be dismissed by men and women in their busyness of life. ‘One more day and I will stop; one more week and I will turn around,’ men and women will find themselves saying and before they realize it, the unprepared will find themselves left behind. ‘The time to turn your lives around is now,’ Jesus tells them, ‘do not delay it for another minute.’