Rarely are fourth installments in mega popular franchises nearly as good as those that came before it. Recent failures like "Indiana Jones and the Kingdom of the Crystal Skull" and "Star Wars: The Phantom Menace" are just two examples of franchises losing their magic on the fourth go round. Thankfully, "Terminator Salvation" bucks the trend and, while not as great as its predecessors, is an enjoyable entry in the series.

"Salvation" takes place in 2018 after the computer system Skynet has destroyed most of humanity in a nuclear holocaust known simply as Judgment Day. The story follows two connected stories: John Conner’s (Christian Bale) mission to shutdown the machines with a computer virus; and convicted murderer Marcus Wright’s (Sam Worthington) struggle to survive while protecting two youngsters he befriends. Their paths converge when Connor discovers one of Wright’s companions is the teenage version of his father.

If you have not seen at least the first two movies in the franchise, do not bother with "Salvation." Like most good franchises, the Terminator films are entrenched in layers of mythology which cannot be easily decoded if entering in the middle.

But for fans of the originals, "Salvation" delivers most everything that might be on the wish list. Huge explosions? Check. Breathtaking effects? Check. A plot full of holes that make your brain hurt if you think too hard about it? Check.

The film does suffer from the lack of Arnold Schwarzenegger’s on screen presence, though he does make a cameo in a very unorthodox way. Bale is a very stiff and robotic version of Connor. Obviously a holocaust can change a person, but he hardly seems like the same person first introduced in "T2." Worthington is perfectly cast as Wright, whose story is by far the most interesting part of the film.

"Salvation" is not a perfect film by any means, but as far as summer entertainment goes, you are not going to get much better.