An unfaithful family man with middle-age crisis becomes the only witness of the assassination of his secret lover while the unknown killer manages to pass it for a suicide.

I will develop it and see where it takes me. I guess the guilt theme doesn't work so well in this story.

Thank you very much for your time FFF, really appreciated!

The new one is very good in my opinion.
good job.

You just mentioned the exact element that I want to develop in the script: guilt. The protagonist would feel guilty for not doing something about the killing. On the other hand, he would try to keep his affaire a secret, but he can't live with the idea of a killer getting away with it (also becuase he really liked his lover). So he would be in a crossroad, until he finds a clue that puts him in the path to discover who the killer is. And then curiosity and justice would push him to investigate.

And yes, by chasing the killer he would be putting his family life at risk, but he can't just let it go and he belives he can uncover the killer and save his own family at the same time (and this would put him under tons of stress).

From your words, I can imagine a better crafted logline like: After witnessing the killing of his lover, an unfaithful family man must find the killer before the police investigation uncovers his infidelity.

I think this sounds great, but the protagonist is moved by a selfish motivation. I like it because it makes total sense, but it's less interesting to me than the guilt theme.

Thanks again!