This 1966 entry in the Godzilla series bucks the "kiddie movie" trend of many late-'60s/early-'70s entries with a surprisingly complex and ambitious plot. In fact, the actual monster mash component of the film is held off until the final hour. In its place, Shinichi Sekizawa's dense yet concise script dishes out a fun spy movie plot that combines a missing brother, a mysterious sea monster, secret military experiments, and a secret hideout driven by slave labor into an energetic and exciting brew. It's a testament to director Jun Fukuda's skills that Godzilla vs. the Sea Monster never gets dull or convoluted: he keeps the action unrolling at a steady pace that allows the plot's turnabouts and surprises to flow in an engaging style. Best of all, the monsters make quite a ruckus when they finally appear -- the battle between Godzilla and Ebirah, the film's villain, includes all the building smashing and boulder tossing a Godzilla fan could hope for (Mothra also makes a guest appearance). In short, Godzilla vs. the Sea Monster probably won't convert anyone who sees the Godzilla series as juvenile, but fans will be pleasantly surprised by its ambitious approach to the giant monster genre.