A weekend turns for the worst for a suave ladies man, when one of his flings harbors a deadly secret.

Maybe include how she reveals what she knows, such as a phone call.
What will happen, or what will he lose if her account is revealed - a wealthy man could lose everything, or a married man losing his family.

"When one of his secret flings threatens to expose a deadly secret, a narcissistic ladies man must..." (Then add to the logline, what the lead must do)