Harold J. Finley (Donald Pleasence) is a mild-mannered college professor on the surface, but after having a brain operation, every time he's angry a stormy cloud emerges and zaps his enemies whether he wants it to or not. For a considerable length of time, he's not even aware it's happening.
The Tropes With the Power:
- An Aesop: Violent thoughts and deadly wishes have consequences when enabled by technology, even beneath the, "kindest, gentlest soul". In other words, Beware the Nice Ones.
- Ambition Is Evil: Dr Keenan and Steve Crandon.
- Asshole Victim: The people attacked and/or killed by the cloud are all rude, dismissive Jerkasses in their dealings with Harold.
- Disproportionate Retribution: However, none of them deserve to die. Harold himself certainly doesn't think so.
- Extreme Doormat: Harold. Deconstructed when being put down triggers an Electric Cloud to appear.
- From Nobody to Nightmare: Harold is a wimpy academic who wields a horrific destructive power without even realizing it.
- Henpecked Husband: Harold can't catch a break with his mean-spirited wife.
- Heroic Suicide: When Harold summons the cloud on himself, it's a combination of this trope, Despair Event Horizon and Driven to Suicide.
- Homage: The concept of the energy cloud (a destructive entity created by a character's suppressed negative emotions) is similar to the Id Monster from Forbidden Planet.
- I Just Want to Be Special: Harold volunteers for the experiment because he wants to break out of his dull, ordinary and unexceptional life, and do something which might make him special.
- My God, What Have I Done?: When Harold realises the effect his subconscious mind has on people, he starts calling himself a "murderer" and resolves to stop Steve's operation by any means necessary.
- Power Incontinence: The premise of the episode.
- Sleeping Single: Dean Radcliffe and his wife Emily sleep in separate beds.