In “Homecoming,” therapy sessions between Ms. Keener and Mr. Isaac, and phone calls between Ms. Keener and her boss, played by Mr. Schwimmer, swirl just around the edges of the central mystery of the story line, twisting closer and closer until its secrets are revealed. The audio-only form frees the story to play with disorienting notions of time, place and identity that might not be possible on film.

The podcast also features sound design by Mark Phillips — who worked on “Serial” and a suite of indie films — that makes it sound more like a movie than the piped-in sound signature of the typical radio drama. Instead of having actors speak into a microphone — a technique used by a lot of early podcasts — Mr. Phillips directed the sound as he would for a narrative film. After an early pilot of the podcast seemed full of dead air, Mr. Horowitz worked in new soundscapes throughout the series. For one scene, Mr. Phillips created a rolling, creaking Ferris wheel that sounds as if it were carrying Ms. Keener and Mr. Schwimmer in and out of the bustle of a street fair. And creating the sound of characters moving as conversations whiz by required him to record noises on location (residents chatting at a retirement home, plates clanging at a diner) and take actors outdoors for external scenes.

“There’s no way to really fake that,” Mr. Phillips said.

But the key to creating a realistic sound lies with the acting. “At the heart of great audio is real emotional truth. I think you can hear it even when you can’t see it,” said Mr. Blumberg. And unlike in a film or television show, there are no visual tricks to support a fine performance in a fictional podcast, or to help hide a poor one.

While these newly ambitious podcasts may constitute big projects for people working in audio, they can feel delightfully indie to film actors. “It felt like making a play for our parents in the garage,” Ms. Keener said.

Plus, the commitment is slight. Ms. Keener recorded for a week; Mr. Schwimmer for just a day. When Ms. Keener convinced Mr. Isaac to come on board, “I said ‘There’s no money,’ and he said ‘Great. Of course. I’m in.’”

Image Oscar Isaac plays an Army veteran in “Homecoming.” Credit... Monica Almeida/The New York Times

Gimlet is one of several companies pushing podcasts forward. The creators of “Welcome to Night Vale” introduced their own fiction imprint this year, Night Vale Presents. Initial offerings include “Within the Wires,” a tale told through relaxation tapes, and “The Orbiting Human Circus (of the Air),” a sprawling project that takes the form of a bizarro variety show; features John Cameron Mitchell, Mandy Patinkin, Charlie Day and Tim Robbins; and was created by Julian Koster of the band Neutral Milk Hotel.