The player takes on the role of a Marine, which didn't get sent to past in time to change the history to a better life. In abandoned city, after when our hero's ally was critically damaged in the previous game the marine travels back to the Earth to try traveling back in time once again... Will fortune smile to him this time?
The text about in the summary section is copy-pasted off of a garry's mod addon called 'Gm_Apartment_Raid_V1'.
Rip-off 'mod', basically.
The guy just took screenshots of addons in Gmod and called it a mod. It's funny that for his "release" he uploaded an archive... with the source code of Nightmare House 2. In fact, there are a lot of similar "mods" on Moddb, it's just that Moddb moderation doesn't pay attention to them.