The conclusion to "Beneath the Planet of the Apes" must have presented considerable problems for Paul Dehn, the screenwriter charged with writing the third part of the monkey franchise. His solution was a rather implausible twist - the primitive ape culture of the future somehow assemble a time-travelling device out of the wrecks of two human spacecraft and send three of their number back to the 20th century.

When Cornelius and Dr Zira (MacDowell and Hunter) arrive in the US, they are initially placed in a zoo. Before long, their ability to talk makes them novelties and eventually celebrities. But when their origins - and Zira's pregnancy - are revealed, the authorities begin to fear that these intelligent and cultured apes may represent a threat to humanity.

Setting the film in contemporary America meant the film makers could concentrate less on spectacle and more on character and plot - which is just as well, since the occasionally shoddy production values reveal a savagely reduced budget. Shorn of eye-candy, the relationship between Cornelius and Zira comes into focus - and it is a believable, compelling, and even touching relationship - despite the clumsy monkey prosthetics.

But while the conclusion is affecting, the plot remains essentially a retread of the first instalment with the roles reversed. As such, it works fairly well as the central movie of the franchise but will have little to offer non-devotees.

Read reviews of all the "Ape" films.

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