Through the Portal

With Lindsey on Izor, Andy must move on with his life with his longtime computer/friend now in the body of a beautiful, green-eyed Irish woman. Lucy, now Rebekah McFarland, is being sought by her brother, Dugan McFarland, an IRA terrorist, along with agencies from around the world who are trying to locate them both. For her safety, Lucy and Andy accompany Colonel Mac to Camp Lookout.
As soon as they arrive at Camp Lookout, they're informed of a recent encounter with a violent UFO they could not identify. Since there is peace with the Izorians, it is suspected the attack came from an Indorian aircraft that had made its way through the portal. The Indorians are looking for a planet that is inhabited by beings that can be used as slaves and with animals that can be used as food.
The future of Earth is now in jeopardy if the Indorian aircraft is not destroyed before communicating with its home planet to guide them to Earth. Earthly forces led by the United States must develop a plan to combat these intruders if they locate the portal and make it through. How can Earth defend itself from an intruder that they cannot track and don't know if or when they'll be encountered?