Likely the Hebrew patriarch Abraham made a deal with aliens, but since he was an ignorant primitive he mistook them for a god. The aliens used their technology to help Abrahams wife have a baby at the age of 90, a miracle. Later when Abrahams decendants were held in captivity by the Egyptians, the aliens helped them escape and guided them to an area with better land and helped them to defeat the original occupants. Around this time they made them the Ark. Many years later one of the aliens named Jesus came to live among the humans teach them how to aspire to be a better race, but they didn't agree with him so they killed him. But aliens prove to be a bit of a challenge to take down, and he got back up, stuck around for awhile and went home, accidently leaving his healing device behind. A couple of thousand years later a guy named Henry Jones Jr. comes into contact with both of the alien artifacts. This summer, he'll get to the bottom of it all.
"I discovered a McGuffin," continues Lucas, still reluctant to name said McGuffin. "I told the guys about it and they were a little dubious about it, but it’s the best one we’ve ever found… Unfortunately, it was a little too ‘connected’ for the others. They were afraid of what the critics would think. They said, "Can’t we do it with a different McGuffin? Can’t we do this?" and I said "No". So we pottered around with that for a couple of years. And then Harrison really wanted to do it and Steve said, "Okay". I said, "We’ll have to go back to that original MacGuffin and take out the offending parts of it and we’ll still use that area of the supernatural to deal with it".