The charm of an old-fashioned inn is momentarily disrupted by a nearby demolition crew gutting the property next door. Mike (Foxworth), the foreman of the crew has trouble keeping his men from going on impromptu breaks and can't account for several of them.
Sleazy gambling czar Tony Fleming (Gordon) is also there trying to purchase the inn so he can turned it into a resort/casino. He, his associate Gloria (Somers) and the various other guests and staff are, like the demolition crew under the grave threat of killer ants with poisonous bites. Not only do the ants kill but they have the sense to flee the scene without leaving any trace that they were there.
In a half-hour plus of screen time the characters finally clue in that something is wrong. Of course it takes them considerably longer before they agree what it actually is and how they can escape.
The acting is not spectacularly bad but only up until they have to interact with swarms of ants and pretend they are afraid they are going to die. Anyone who lives on the side of a hill can tend to get the ant swarm horror in their basements during the summer.
Producers rounded up a huge cast of ants to appear as extras in this film (If I had been their agent I'm sure I could have at least gotten them scale) and the result is what looks like millions of the little buggers. Sometimes realism is cheaper than special effects or staging tricks.
It makes for fairly entertaining high camp and great 1970s B-movie fun. Improbable and illogical but no more so than any Hollywood movie. It is still enjoyable horror/suspense kitsch with a highly predictable ending even for a TV movie.