Inspired by Berzerk, Shamus, a 21st-century robo-detective, must travel a maze of 128 screens to find and destroy the evil Shadow (himself an Expy of Evil Otto). He must find the right keys to unlock doors, collecting "mysteries" that give points or extra lives (or summon the Shadow), and defeat many, many enemies. You're equipped with an unlimited supply of "Ion-SHIVs", laser throwing knives that can vaporize nearly any enemy in your path.
Followed by a very hard-to-find sequel, Shamus: Case II.
- Deadly Walls: Touch any wall and YOU ARE DEAD.
- Everything Trying to Kill You: Everything, including the walls.
- Evil Is Angular: The "good" Shamus is curved like a humanoid, but the "evil" Shadow has a squarish face and stick-like appendages.
- Expy: The Shadow is one, of Berzerk's Evil Otto. Both are fast, unbeatable stalkers that will chase you out of a Deadly Walls maze (and they ignore said walls) if you don't leave fast enough.
- Friendly Fireproof: Averted with the mooks. Their bullets are as deadly to them as you.
- Fun with Acronyms: Your "Ion-SHIV", a.k.a. the "Ion Short High-Intensity Vaporizer".
- Hitbox Dissonance: In the Atari and Color Computer versions, it is entirely possible for horizontal enemy bullets to pass safely through the space between the hat and the head.
- Ninja Pirate Zombie Robot: You're a robotic detective.
- One Bullet at a Time: Depending on version, you can have up to two Ion-SHIVs on the screen at once.
- One-Hit-Point Wonder: Both you and the enemy mooks die in a single poke.
- Spiritual Successor: Of Berzerk. Both involve mazes with deadly walls filled with robots, in which a stalker will chase you out if you don't leave fast enough. Unlike Berzerk, this is not an Endless Game.
- Stalked by the Bell: The Shadow. If you don't exit a room fast enough, the Shadow will chase you out.