It is day 38 of a 39-day game of the reality television show “Survivor,” and Ashley Underwood, a beauty pageant winner from Benton, Maine, is still competing for a million-dollar prize in the blistering heat of the Nicaraguan jungle.

Underwood has an intense look of concentration on her face. She has lived with belligerent strangers under extreme conditions and is mentally exhausted. Her gaunt frame is stark evidence of the 20 pounds she has lost since she first said goodbye to her family and boarded the plane to meet with the show’s producers.

In this challenge against her three final opponents, the stakes could not be higher. The winner will automatically enter the finale, where a group of eliminated players will vote on who should receive the money.

The task is simple: The first person to navigate the giant maze and solve a word puzzle at the end, wins.

The scrappy Underwood is the only real threat to the dominance of four-time-player “Boston” Rob Mariano, 34, a former construction worker who has orchestrated nearly every elimination throughout the game. Mariano would have used his clout to eliminate Underwood sooner, but she has protected herself by winning the two previous challenges. She needs just one more miraculous win.

“Survivors ready — Go!” shouts host Jeff Probst, as he does every challenge of every season.

She sprints into the maze first, the other players crowding behind. She and Mariano quickly distance themselves from the pack, zipping to various stations, collecting puzzle pieces, Mariano always a few steps ahead. When they arrive at the final stage, a solving station in the center of the labyrinth, Mariano’s lead is just seconds. He frantically dumps his puzzle pieces out of cloth bags and tries to figure out the answer, the four-word phrase “only you are safe.”

Underwood quickly solves two words, and Mariano, sensing he is behind, asks her with just a hint of desperation if they can work together, based on a supposed alliance between them that neither of them trusts. She rightly declines. It seems she has little to win and everything to lose.

Seconds later, she has stalled while he picks up speed. He jumps into the air, arms upraised in victory while the host calls his name. Underwood’s brow furrows. A million dollars may have just slipped through her fingers.

Ask Underwood today whether she has any regrets about her 39 days in Nicaragua, and one thing comes to her mind.

“I would have done the last challenge differently,” she said.