What is the title of the Desmond-centered fifth episode of Lost season 4?

What is the title of the Desmond-centered fifth episode of Lost season 4? It is “The Constant.”

“The Constant” is the fifth episode of Lost’s fourth season and the 77th episode of the series overall. It aired on ABC on February 28, 2008, and was written by Carlton Cuse and Damon Lindelof, with Jack Bender directing.

The episode follows Desmond as he suffers a dangerous form of time displacement after traveling to the freighter. His consciousness shifts between 1996 and 2004, leaving him unable to distinguish past from present. Daniel Faraday helps him understand that he must find a “constant”—a person or object linking his different states of consciousness.

Penny Widmore becomes the crucial emotional anchor when Desmond contacts her by telephone. The episode is often remembered for combining high-concept science fiction with the couple’s long-running love story. “The Economist,” “Eggtown,” and “The Other Woman” are neighboring season-four episodes, but none is the Desmond-centered fifth installment.