Based on the 2001 version; the 1999 version has never been released on home video in any market.
In Southeast Asia, Dr. Campbell, Richard Livingston and Dr. Hughes lead an archaeological party exploring deep caverns. Hughes is separated and discovers an alien corpse with a fossilized diamond, while Campbell uncovers hieroglyphics pointing to the location of a dinosaur skeleton. Two years later, an alien mothership arrives near Earth's orbit and destroys two American satellites, drawing the attention of the UNDA. A photojournalist named Bud Black learns about a dinosaur dig led by Campbell and his assistant Holly Davis.
Hughes, who has been believed dead, arrives at the dig site to warn Campbell about the dinosaur's resurrection, but is quickly removed from the site. The alien ship sends beams to reanimate the dinosaur, killing several diggers. Holly confronts Campbell about the mysterious deaths and quits after Campbell refuses to launch an investigation. Hughes finds Holly and reveals to her about the Yonggary legend, the alien fossil, and that he was held by the U.S. government as a "guest" for the last two years. She initially dismisses his claims, but comes around after he shows classified data concerning the alien fossil.
They return to the dig site to stop Campbell, but arrive too late when the alien ship fully resurrects Yonggary, killing Campbell in the process. The alien ship dematerializes Yonggary. Holly and Hughes are taken into custody by Parker. Yonggary is then teleported before them and escapes before a helicopter squadron engages Yonggary in battle, only to be defeated. The NSIA sends Stanley Mills to share information regarding the aliens with General Murdock and General Howell. Mills explains that a paleontologist provided the NSIA with scientific evidence that an alien civilization visited Earth 200 million years ago and that vital information in defeating the aliens was stolen. Mills recommends to capture the aliens alive, but Howell wishes to destroy them. Yonggary is then teleported to Los Angeles and proceeds to attack.
Upon arriving at the UNDA base, Hughes and Holly are confronted by Mills, who reveals that Hughes was the paleontologist who shared his discoveries and later stole information from their lab. Hughes counters that he warned the NSIA but chose to ignore him. Mills attempts to take the stolen data disc back but fails and is detained. The US President gives the UNDA five hours to defeat Yonggary or will launch a nuclear strike. Murdock orders General Thomas to dispatch his experimental Project T Forces, led by Parker, to attack Yonggary.
Hughes and Holly decode the additional hieroglyphics and uncover that the aliens are controlling Yonggary through a diamond-shaped receptor on his forehead and that "another great light will be sent to do battle." Failing to defeat Yonggary in time, the President sends a bomber to kill Yonggary, to Mills' delight. The T-Forces manage to break the aliens' control over Yonggary. Mills tries to convince Murdock to kill him but is ignored, which forces Mills to jam the UNDA's radars unless they let him leave. Mills fails and is arrested. The aliens send a new monster, Cycor, to battle Yonggary. Cycor initially gets the upper hand, but Yonggary emerges victorious in the end, forcing the aliens to flee. The generals manage to stop the bomber at the last minute and the following morning, the UNDA transports Yonggary to a deserted island, where he can live in peace.
> another great light will be sent to do battle
