2x05 A Single Blade of Grass, written by Erin Maher, Kay Reindl and Michael R. Perry, directed by Rodman Flender.
A good opening: an ominous Native American ceremony with men in scary masks. One throws the runes and gets a bad result. He is made to drink snake venom and has visions. The camera pulls out and we see we are in an underground place. Up the stairs into a luxury hotel in New York with the Twin Towers on the skyline.
Frank arrives to investigate a fresh body found at an archeological site which is holding up construction. He learns that Indian spiritual seekers are paralleling his own journey, using their own symbology. He cries when he realizes this.
The Indians come to believe he has been called to fulfill a prophecy (as in Last Wave, The (1977)) and he is forced into the ceremony and drinks snake venom (which reminds me of the Yaqui mushrooms in Altered States (1980)).
This might have built to something important but it is suddenly wrapped up in a terrible clownish ending.
It would have been better to let them believe in their prophesy (and let Frank live, of course). Else he would have had to convince them of his version: that the apocalypse is terrible, not hopeful.
The Indian sage is played by Floyd "Red Crow" Westerman -- Dances with Wolves (1990), Clearcut (1991), Hidalgo (2004) and five episodes of The X-Files.
Frank says he is one-eighth Crow.