Walter's (Woody Strode) prize calf dies mysteriously, the local cowboy vet Dr "Rack" (Shatner) investigates. With the cause of death a mystery he calls in expert Diane (Tiffany Bolling), though as she is a girl Rack seems to have trouble taking her seriously, or is more interested in getting into her pants than anything else. Basically this is Captain Kirk in a Stetson.
Diane discovers that the calf was killed by incredibly potent spider venom, soon tarantulas are everywhere and people are dying fast. Rack, Diane and a few others end up holed up at a lodge surrounded by millions of tarlantulas...
This is a standard spider attack film, including plenty of shots of people opening hatches above their heads (for some reason) and spiders falling on them. Shatner is Shatner, which will probably make or break the film for you. I think its great, even though i hate spiders!