• Ross Hunter's new musical remake of LOST HORIZON is a dull epic, full of incongruities and barren stretches in which nothing much happens. The only good part of the movie is the first half hour, during which members of a relief mission escape a band of guerrillas in Southeast Asia, only to be hijacked and flown to a remote area of northern China. The style and tone of this part of the film is reminiscent of Ross Hunter's earlier epic, AIRPORT. The movie begins falling apart when the group reaches Shangri-la, an "ideal society" cut off from the rest of civilization. In this seeming paradise, the sun shines warmly all year around, disease is unknown, and nearly everyone lives to a ripe old age. Society is divided into two broad classes: a mass of happy, simple-minded peasants who perform the manual labor, and a group of monks who govern Shangri-la and devote their lives to intellectual and religious contemplation. Socially, it resembles Plato's conception of a country ruled by "philosopher-kings," and the fact that it seems so stagnant and lifeless may say something about the practicality of such benevolent dictatorships. Galt's Gulch it's not. The sense of being in some exotic foreign land is destroyed by Burt Bacharach's bouncy score and the banal lyrics of Hal David. The incongruities of the script and awkward musical transitions make it impossible to judge the performances fairly; the actors seem to struggle along as best they can. None of the characters is fully developed, and motivations are often impossible to decipher. Peter Finch attempts to be thoughtful, but comes off instead as weak and indecisive. Michael York, as Finch's younger brother who wants to escape, seems to be the most intelligent person in the film. Sally Kellerman is frantic as a suicidal war correspondent, Liv Ullmann uninteresting as the schoolteacher. Olivia Hussey registers well as a Shangri-la native with a fatal desire to discover the real world. The musical sequences range from spectacular to corny, mostly the latter. With different premises and more conflict, LOST HORIZON might have succeeded, but as it stands it's chiefly valuable as a cure for insomnia. Rated "G".

• SLITHER is an insane movie, an adventure-comedy populated by such kooky characters that it's often hard to concentrate on the plot, which is alternately hilarious and suspenseful. James Caan, in a departure from his violent role in THE GODFATHER, plays an ex-convict attempting to trace some money embezzled by one of his prison buddies, since deceased. His erstwhile cohorts are Sally Kellerman, a freaked-out blonde with a passion for the beach and for armed robbery; Peter Boyle, the embezzler's partner who's an outdoor enthusiast; and Louise Lasser, Boyle's wife, who once had a high-school crush on Caan. On their way to recover the money, the four encounter a succession of equally offbeat people and events, and are pursued by a mysterious (and appropriately frightening) black van, culminating in a wild chase scene. The performers play their freaky roles to the hilt, keeping the film moving at a fast pace. The script by W.D. Richter is full of clever dialogue, and has some fun with the audience in the opening scenes: For about 15 minutes, it's impossible to tell when the events are taking place. At first it seems like the 1930's, then the 1940's, then the early 1950's. It all occurs so naturally that it takes the audience a while to realize it's being conned. But it's all good, mostly clean fun. Rated "PG".

• THE THIEF WHO CAME TO DINNER is a sometimes amusing, sometimes flat crime caper film with just enough inventiveness to keep it from becoming tedious. Ryan O'Neal stars as a computer programmer who abandons the world of "corporate crime" to become a burglar because, as he puts it, it's "more honest." Jacqueline Bisset, his partner in crime and other events, walks through her part without a trace of visible emotion. Warren Oates creates an effective and sympathetic character as Ryan O'Neal's nemesis, a hapless but dedicated insurance investigator. Like most films of its type, THE THIEF WHO CAME TO DINNER has a gimmick. Each time O'Neal commits a burglary, he leaves a chessman as his trademark. This earns him the nickname of the "chess burglar," and eventually evolves into a battle of wits with the chess editor of the local newspaper, who challenges him to a match. Austin Pendleton is delightful as the temperamental, prima donna chess editor, Zukovsky. The remainder of the plot is fairly predictable, and the film's cool detachment inhibits anything more than superficial audience involvement. THE THIEF WHO CAME TO DINNER is a pleasant diversion, and nothing more. Rated "PG".