When his mysterious girlfriend rejects his marriage proposal, a bewildered man conducts a secret investigation to discover why.

Anthony,

I'm not sure that mentioning "mysterious girlfriend" is enough or even appropriate here. For him to offer marriage, she must be somewhat un-mysterious, don't ya think?

Tell me something interesting about this investigation, stakes, time frame he has, ext...

May want to begin this with: "After his marriage proposal is rejected, a bewildered man...."

Perhaps mention his internal struggle to overcome this rejection. Is the girlfriend a super model or something? Why is unwilling to give up on her after she gave up on him?