Underground

An underground city built millions of year ago. When a meteor hit earth and killed the dinosaurs, a ship observing from an ancient highly advanced civilization got caught in the gravity and crashed. Many survived, but due to the blocked sunlight and highly toxic cloud from the impact had to go underground. They survived and built a huge, golden, underground city that lasted for thousands of years. Due to unknown circumstances, they lost the ability to reproduce. Many years went by and many died until there were only a few dozen left. The experimented with animals that looked similar to them and tried to combine their DNA with them. Before the results were known, they had to go into hibernation to preserve the handful of survivors.

Now, in our time, a battered wife, running away from a drunk husband, ends up in an underwater cave in the Rio Grande River. She finds a trinket that appears to be gold. She sells the trinket in Mexico. Drug dealer find out about the trinket and force her to reveal her place of discovery. They find nothing, but a blue door that they cannot open or destroy. Brad Staples buys the trinket and it's millions of year old. Will he get past the door and discover the underground city.