Once the adulteress has caught the fool in the trap of his own ungodly sexual desires - she then informs him of his soon-to-be-committed adultery. At this point, the man is so entrapped, that he is no longer considering sin - but the ability to not get caught.
She says to him that her husband is not at home - but is gone on a long journey. Evidently her marriage means nothing to her. Long gone are the words of her covenant to God - or any real love for her husband. Instead she is interested in her next sexual escapade or conquest. Her words betray her husband - and also betray that she cares nothing for her own spiritual condition, or that of her sexual prey. Her focus is on neither of them getting caught - in this world. In verse 19 she even knows the approximate time he is coming home. Therefore she can sin unfettered until that time. She even uses her treachery to lure the fool in closer. She is utterly blind to the fact that God sees all this - and they are caught - NOW!
Think for a moment of David. He thought no one saw him lusting for Bathsheba on his rooftop. He thought that only a few knew of her coming to his chambers - and none of them actually knew if they committed adultery. Then, when she became pregnant, he thought that no one knew of his treachery of bringing Uriah from the midst of a battle to cover his tracks. When that did not work, he thought only a few knew of his plan to kill Uriah - and try to legitimize his adultery by marrying his widow after murdering him with an enemy army. But the fact was David was caught the moment he sinned in his heart. It was along the way that more people knew - and if you understand the nature of gossip - far more knew than he thought.
Covering our sin does not work. David said after his sin that he who covers his sins will not prosper. He spoke of how he suffered when he hid his sin - how the work of the Holy Spirit convicting him and sapping his very strength as he tried to keep things hidden was strong. Sin will try to deceive us of its very existance in our lives. It will tell us that we have NOT sinned. It will tell us that we are FINE. But all along the way are lies. The wise man is the one who knows that trying to hide sin is the most foolish act in which a person can engage. God is omniscient and sovereign - that is absolute fact. This means that there is nothing we can hide from Him - even for a second. It also means that all our attempts to maintain our sin are superceded by His sovereignty. Man may plan his steps - but God ordains his way. While that does not mean that God makes us sin - it does mean that His discipline WILL prevail when we do - no matter what we think we are doing to stop it.