Early one morning a young man (Timothy Bottoms) sets up his fishing equipment on a Californian pier, but he's not interested in catching anything. He is actually staring through his binoculars at someone doing maintenance on a rollercoaster at a nearby fun park, and that night he enters the park and begins to wander around, partaking of the amusements and acting natural. Yet he is anything but a normal customer, as he has been here earlier on that day and set a device up on the rollercoaster, an explosive which he will trigger later on - but nobody could be that callous, could they?
Oh yes they could, and this psychopath who also happens to be a technical genius is our villain. We never find out his name or even his true motives other than the financial one, but you come to see him as taking pride in outsmarting the authorities, and that could be his main impetus. This was lumped in with the then-fading disaster movie genre when it was first released, but actually where that type of film concentrated on a number of characters and their lives to offer us that essential human interest angle, here we're only interested in one person.
That person is Harry Calder, played by George Segal with that brand of world-weariness that he carried off so well. Harry is a safety inspector, and he is called by his boss (Henry Fonda in the kind of role he spent most of the seventies taking) to find out what happened when the rollercoaster we saw in the opening crashed and killed the passengers, a nasty sequence which does well to resonate throughout the rest of the film. Harry begins to have his suspicions about foul play when later that week he hears of an amusement park fire; no one killed there, but strange enough not to be a coincidence.
Soon he is on to the mad bomber, and being the sort of man who can be a pain in the neck to even people who like him, Harry is determined to prevent any more loss of life and wheedles his way into a top secret meeting to discuss the blackmail plot. This gets him noticed by the villain and we begin to see how underrated a thriller this is as director James Goldstone, best known for his television work (he directed the first episode of the original series of Star Trek), tightens the screws of tension. The centrepiece of this is not a rollercoaster tragedy, but a lengthy sequence where Harry is chosen to deliver the ransom at one of those parks.
This marks out the bomber as a man to be reckoned with as he effortlessly outwits Richard Widmark's F.B.I. man, and although the feds believe they have the upper hand, something which turns out to be a potentially deadly mistake. Then comes the climax, drawn out over a palm-sweating half hour, where there is a race against time to find a bomb without panicking the public at a park where a brand new ride is being premiered. Segal does very well out of this in an enjoyably sardonic and exasperated performance, reminding us what an underestimated star he was, and there are plenty of details to catch the eye, such as Sparks playing at the park and Ron Mael looking as if he'd rather not be taking part until he smashes up his piano stool. Rollercoaster may be regarded as gimmicky now, and it did utilise Sensurround to enhance its sound in cinemas, but it's actually a very professional, well crafted thriller of the type this era did so well. Music by Lalo Schifrin.