The show centers on FBI special agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) who work on cases linked to the paranormal, called X-Files.

In this episode, Scully learns that she, but not Mulder, is being given a chance to prove her worth at the FBI, and—paired with a new partner—she investigates a crime scene photographer with an uncanny knack for arriving just in time to see his victims' final moments.

The episode was based on three different stories: Arthur Fellig, the Greek myth of Tithonus, and the yellow fever epidemic in the 19th century.

As the man reaches the basement, the cab crashes and its door spills open to reveal the woman's wrist, covered with blood.

Later, in Washington, D.C., FBI Assistant Director Alvin Kersh (James Pickens, Jr.) assigns Dana Scully (Gillian Anderson), along with Agent Peyton Ritter from New York, to the case.

Scully and Ritter soon discover that their prime suspect, Alfred Fellig, who has worked as a police photographer since 1964, has not aged at all in any of his official photos on his renewal applications.

When he approaches to take photos of the dying young man, the murderer returns and repeatedly stabs Fellig, but he pulls the knife out of his back and walks away.

Scully leaps out of the car with her gun, announcing that she is an FBI agent and handcuffing the pimp, but when the prostitute tries to flee, she is hit by a truck and killed.

In his darkroom, Fellig shows Scully a photo of a dead woman with an odd fuzzy shape around her head, which the photographer claims is Death.

Going inside the room, Mulder reports to Scully that Fellig died of a single gunshot wound, while the doctors are amazed at her own rapid recovery.

Frank Spotnitz, the show's executive producer, claimed that the breakthrough came when they began contemplating the idea of an immortal photographer trying to catch Death so that he could die.

The third and most fantastical inspiration was the Greek myth of Tithonus (to which this episode's title alludes), who was the son of Cephalus and the lover of Eos, Goddess of the Dawn.

The season three episode "Clyde Bruckman's Final Repose" featured Scully being told by the titular character that she would not die.

[6][7] Several of the scenes for "Tithonus" were shot on the sound stage of NYPD Blue, an ABC program whose sets were just across from the Fox studios.

[8] All of Fellig's cameras were borrowed from the University of California's Museum of Photography, and many of the photographs were used courtesy of the Los Angeles-based advertising and licensing agency Corbis.

The production staff of The X-Files was tasked with not only creating the photographs that Fellig takes, but also with ensuring that each looked as if it belonged to a discrete time period.

Tom Day, the episode's property master, researched "popular government typefaces and printing technologies" to make the pictures as historically accurate as possible.

[8] Besides a direct reference to the titular mythological character, Matthew VanWinkle, in the chapter "Tennyson's 'Tithonus' and the Exhaustion of Survival in The X-Files", of the book The X-Files and Literature: Unweaving the Story, Unraveling the Lie to Find the Truth, argues that the episode bears a striking resemblance to Alfred, Lord Tennyson's dramatic monologue "Tithonus".

"[9][10] VanWinkle argues that in The X-Files episode, this line is paralleled by Alfred Fellig's tendency to see those about to die in a monochromatic vision.

VanWinkle also notes that Fellig is, furthermore, different from Tennyson's Tithonus because the latter actively sought immortality, due to the flaw of hubris or extreme pride, in order to become more like a god.

[21] Tom Kessenich, in his book Examination: An Unauthorized Look at Seasons 6–9 of the X-Files wrote positively of the episode, comparing it favorably to "Clyde Bruckman's Final Repose".

"[22] Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode five stars out of five, drawing comparisons to "Clyde Bruckman's Final Repose", but noting that the former has "a flavour all of its own".

Shearman and Pearson praised Geoffrey Lewis' portrayal of Fellig, and described "Tithonus" as "bizarre, chilling, and yet strangely life-affirming".