Threshold is a 2003 Sci Fi Pictures original film adaptation of the 1958 black and white science fiction film

Science fiction film

Science fiction film is a film genre that uses science fiction: speculative, science-based depictions of phenomena that are not necessarily accepted by mainstream science, such as extraterrestrial life forms, alien worlds, extrasensory perception, and time travel, often along with futuristic...

 It! The Terror from Beyond Space

It! The Terror from Beyond Space

It! The Terror from Beyond Space is a 1958 black and white science fiction film directed by Edward L. Cahn.-Plot:The film opens with a nuclear-powered spaceship perched on the cratered surface of an alien world. A voice-over tells us that the year is 1973 and that this is the planet, Mars. This...

 (directed by Edward L. Cahn). The film stars Nicholas Lea

Nicholas Lea

Nicholas Lea is a Canadian actor best known for his portrayal of Alex Krycek on The X-Files and on Kyle XY playing Tom Foss.-Biography:...

 (The X Files' Krycek

Alex Krycek

Alex Krycek is a fictional character in the long-running American science fiction show, The X-Files portrayed by Nicholas Lea. Initially introduced in the second season as a partner for main character Fox Mulder in the absence of his previous partner, Dana Scully, Krycek grew to become one of the...

), Jamie Luner

Jamie Luner

Jamie Michelle Luner is an American television actress, best known for her role as Lexi Sterling on Melrose Place and Rachel Burke on Profiler...

 (Melrose Place's Lexi Sterling), and Steve Bacic

Steve Bacic

Steve Bacic is a Canadian actor of Croatian origin. He is known for playing the character Telemachus Rhade on the Sci-Fi series Gene Roddenberry's Andromeda. After being a guest star in season 1-3, he joined the cast early in season four...

 (Gene Roddenberry's Andromeda

Andromeda (TV series)

Andromeda is a Canadian-American science fiction television series, based on unused material by the late Star Trek creator Gene Roddenberry, developed by Robert Hewitt Wolfe, and produced by Roddenberry's widow, Majel Barrett Roddenberry. It starred Kevin Sorbo as High Guard Captain Dylan Hunt...

). Other notable cast members include Teryl Rothery

Teryl Rothery

Teryl Rothery is a Canadian actress. She is best known for her role as Dr. Janet Fraiser on Stargate SG-1.-Life and career:Rothery was born in Vancouver, British Columbia...

, television mogul Stephen J. Cannell

Stephen J. Cannell

Stephen Joseph Cannell was an American television producer, writer, novelist and occasional actor, and the founder of Stephen J. Cannell Productions.-Early life:...

 (as Pacheco Laval), and Gloria Slade.

Plot

The crew of the space shuttle Oklahoma comes back to Earth, one of its crew members having been struck in the arm by a tiny meteor, which evidently contains alien life forms. This alien life parasitizes its human hosts to evolve into rapidly proliferating insect-like creatures. The Oklahomas chief medical officer (Lea) works to stop the spread of the infestation before it reaches the "threshold" population, at which humanity will be effectively unable to contain it and the alien life will take over.