THAI JACK

In "Stranger in Strange Land," wandering Jack is in Thailand with a mysterious woman named Achara. She gets involved with Jack, who is on an alcohol-drug binge. The woman almost has a shaman effect on Jack.

The tattoo that Achara designed on Jack's arm translates to "He walks among us, but is not one of us."

Who walks among us but is not one of us?
A foreigner? A spy? A conqueror? An agent for destruction?

If "us" refers to humans:

Ghosts? Spirits? Angels? Demons?