You are Catherine Dubont. The Laser Drill opened a cavern 10 miles beyond the surface of the earth. They installed an elevator which you and some others took to go down all the way into the world of the unknown. As you almost reached the bottom of the drill hole, the elevator rope broke and the cabin dropped down the last 100 feet. Everyone is dead. All lights are gone. The only thing you have left is your modern sonar scanner.
This game does so much right that I really wanted to give it higher rating. It does an amazing job of creating a tense atmosphere at all times. The minimal graphics force you to listen and respond to the sounds. I found myself picturing in my head what the cave looked and felt like, which I imagine one would actually have to do if they were trapped in a cave with nothing but a sonar. However, I found sneaking past the enemies almost imossible at times. The rock throwing is great conceptually, but most the time I found it incredibly difficult to successfully distract the enemies. For instance, an enemy could use its own sonar like ability to detect me from around a corner half way across the screen, but they only seem to hear the rocks when the rock hits a wall nearly right next to them. At that distance, distracting an enemy with a rock seems pointless. Most of the game is designed really well, and it is worth at least trying the demo. If the enemy AI is improved with SONAR+, I would highly recommend this game.