Interesting story, but honestly not very believable. You know nothing about these characters and suddenly one of them is telling the other a secret, and it sounds as if the only reason he's telling him is so that the reader knows what's going on. It sounds very fake. And the whole thing is over in a few lines. This could hold much more interest and imagination and intrigue, but it's just lacking.

Then suddenly it jumps to midnight - this has no connection to anything. Is he asleep, is he up working? The footsteps might be pivotal to the plot or a minor thing but it should have a backdrop, otherwise there's no suspense in it, it evokes no interest.

(Also, if you want to have one story, it's better to just put the prologue and chapters together instead of on two seperate pages.)

All in all, this is interesting, but it's lacking in many ways and doesn't evoke interest or suspense in the reader, which is what a mystery should be doing within the first few pages.