Most stories are easy. 'Kill everyone that isn't you' is as far as most games go.
Occasionally there's a little motivation thrown in, stuff like 'they killed your father/girlfriend/puppy, now make them pay'.
But generally you're not going to find thought-provoking depths to analyse - obviously the auto-shotgun symbolises the protagonist's growing sense of inadequacy. Every now and then, however, a game comes along with a script that feels like 20 people shouting at you all at once; a mess of sub-plots, timelines and twists that gives you an instant headache.
So consider this your one-stop cheat sheet to the hardest plots out there. All explained for you to understand with the minimum of pain. Oh, and there will be spoilers.
Platforms: PS1, PS2, PS3, Xbox 360
The Umbrella Corporation is formed to research the Progenitor Virus, exploiting its powerful mutagenic properties to create bioweapons. During the late '90s a viral outbreak around the research facility is investigated by a military unit called STARS.
A second outbreak sees Raccoon City consumed by zombies while a bioweapon called Nemesis is released to hunt down STARS members. By 2003, Umbrella is destroyed and their research leaked globally.
A year later, the Las Plagas, a mind-controlling parasite, is discovered when a cult attempts to infect the US president. The Bioterrorism Security Assessment Alliance (BSAA) is formed to combat biological terrorism.
An outbreak of engineered Las Plagas in Africa uncovers a forgotten Umbrella research site and the source of the original virus. Using the information uncovered, Umbrella scientist Albert Wesker develops a new virus called Uroboros, intending to release it and create a new world order. He's defeated and incinerated in a volcano.
Platform: PS2, PC
JC Denton is a nanotechnologically augmented member of the United Nations Anti-Terrorist Coalition (UNATCO). He's sent after a terrorist group who have apparently been stealing Ambrosia, a vaccine for a virus called the Gray Death. JC is told by his brother Paul that UNATCO engineered the Virus and are using it to control the world.
JC is then contacted by the remains of the Illuminati, a failing secret government, their splinter group, Majestic 12, and Daedalus, a rogue Illuminati AI. JC destroys the machine creating the virus, during which time Daedalus merges with a Majestic 12 AI called Icarus to form Helios, a third AI that plans to govern the world as a benevolent dictator.
There are three possible endings - JC can destroy global communications plunging the world into a new dark age; return the Illuminati to power or merge with Helios. The sequel Invisible War uses the final option as cannon.
Platform: PC, Xbox 360, PS3
The underwater city of Rapture is built by Andrew Ryan as a place for art, science and industry to fl ourish. When ADAM, a DNA-altering material granting people special powers, is discovered, a war breaks out between Ryan and Frank Fontaine, a powerful mobster/businessman.
Fontaine buys the embryo of Ryan's illegitimate son and accelerates his growth. Ryan's son, now called Jack and fully grown, is programmed to kill his father, imprinted with fake memories and sent to America.
Unaware of his origins, Jack is unconsciously controlled by the phrase 'Would you kindly'; words that appear on a card from his 'family' during a transatlantic flight, causing him to hijack and crash the plane over Rapture.