A poor young man working in a skid row flower shop, Seymour, falls for a pretty blonde, Audrey. After a solar eclipse, a wird plant appears in the shop. It's reminiscent of a Venus flytrap in appearance. It grows and grows.
Turns out it's from a place far away, is highly intelligent and also carnivorous, with a thirst for human blood. The strange plant makes the flower shop popular and financially viable, and Seymour finds himself manipulated from multiple directions.