Underhell is a Source Engine game developed by the Underhell Team in collaboration with We Create Stuff. Underhell Chapter 1 requires ONLY Source SDK Base 2007 installed. No Source game is required.

Berlot7 says

8/10 - Agree (4) Disagree (1)

Enjoyed it a lot. I was confused on occasion on what I was supposed to do next or where to go. Especially in chapter 1. For instance, finding the building across from the hospital entrance or where to go in the parking deck after reaching the top. Reminded me a lot of F.E.A.R.