In a grim and ugly future, the year 2022, a venal cop (though no worse than the rest and better than most) investigates a murder. It looks like an assassination. Nothing was stolen even though the corpse was rich and his apartment opulent beyond the wildest dreams of the masses of people living in poverty on the streets below. Did some sinister power need to keep this man quiet? What didn't they want him to say? Detective Thorn (Charlton Heston) has the help of his 'book', Sol (Edward G Robinson) who, lacking any high-tech resources such as computers, consults books and his old friends at a sort of information exchange facility. Everything is in short supply except humanity. Food and water is short, accommodation, power, clothing, paper - everything - and every space is filled with the swarming, desperate masses. Thorn finds a couple of weighty tomes in the dead man's apartment and passes them to Sol who almost swoons with delight at the sight and feel of real, solid, beautifully bound books. He takes them to the exchange and he and his friends mine their resources for information. What they find is unbelievable, horrible, repellent. Sol is moved to do something extreme, both to relieve his shattered mind of the intolerable shock and to lead his friend Thorn to irrefutable proof of the terrible truth.The film was made in 1973 and it must be one of the earliest environmentalist stories to have a go at man-made global warming. Pollution is killing the oceans. The climate has heated the land, making farming unproductive. Winter has been obliterated by the 'greenhouse effect'. The only food most people can get hold of is a kind of biscuit called 'soylent'. It comes in three tasteless varieties: soylent red (ingredients unknown), soylent yellow (soya) and soylent green (plankton). However, as the oceans have been poisoned, the plankton is dying - so what are they really putting in the soylent green? It's grisly. It's gripping.