It sounds like the pitch for a creepy science-fiction or horror movie: two astronauts stranded in space. But for Sunita "Suni" Williams and Barry "Butch" Wilmore, who are currently stuck on the International Space Station, the situation isn't nearly as Hollywood-scary as that. Let's break it down.

Who are the astronauts?

Wilmore, 61, and Williams, 58, are veteran astronauts -- both naval officers and former test pilots. Williams has been a NASA astronaut since 1998, and Wilmore since 2000. Both have plenty of experience in space.

Williams is the former record holder for most spacewalks by a woman (seven) and most spacewalk time for a woman (50 hours, 40 minutes), and in 2007 ran the first marathon by any person in space.

In 2009, Wilmore piloted the Space Shuttle Atlantis on its mission to the ISS, and in 2014, was part of the ISS crew that used a 3D printer to manufacture a tool -- a ratchet wrench -- in space, the first time humans manufactured something off-world.

What is their mission in space?

Wilmore, as commander, and Williams, as pilot, traveled to the ISS on a 15-foot-wide, Boeing-made capsule called Starliner. They launched on June 5 and docked with the ISS on June 6. NASA hopes Starliner will give the organization a new way to get crews to and from the ISS, and the fact that it's Boeing-made is another sign that NASA is starting to lean on the private sector for its human spaceflight options, The New York Times reported. 

Wilmore and Williams' ISS mission was supposed to last a mere eight days, during which they'd test out aspects of Starliner and see how it operates with a human crew in space. But due to complications with Starliner, the two astronauts are still up there, and won't be back before 2025. They've kept busy -- working with the ISS Expedition 71 crew to perform research and maintenance activities, NASA said.

How did they get stuck in space?

The Starliner was delayed in May due to a problem with a valve in the rocket. Then engineers had to fix a helium leak. That's all bad news for Boeing, which is competing with SpaceX, which has been transporting astronauts to the ISS since 2020, making over 20 successful trips to the space station.

Starliner finally launched, atop an Atlas V rocket, on June 6, but some problems came along with it. NASA announced that three helium leaks were identified, one of which was known before flight, and two new ones. In addition to the leaks, the crew had to troubleshoot failed control thrusters, though the craft was able to successfully dock with the ISS. 

SpaceX has had failures, too. A Falcon 9 rocket exploded on the launchpad in 2016. And in July, a Falcon 9 rocket experienced a liquid oxygen leak and deployed its satellites in the wrong orbit, The New York Times reported. But that said, SpaceX has more than 300 successful Falcon 9 flights to its credit.

The astronauts are safe

NASA has been quick to report that the astronauts aren't in danger, nor are they totally stuck. 

"There is no rush to bring (the) crew home," NASA said in a statement last week. "This is a lesson learned from the space shuttle Columbia accident. Our NASA and Boeing teams are poring over data from additional in-space and ground testing and analysis, providing mission managers data to make the best, safest decision on how and when to return crew home."

On Saturday, a decision was reached.

When and how are the astronauts coming home?

NASA said last week that it's decided to return Starliner to Earth without a crew, probably in September, and then bring Wilmore and Williams home on the SpaceX Crew-9 Dragon spacecraft early next year.

"Wilmore and Williams will continue their work formally as part of the Expedition 71/72 crew through February 2025," the space agency said in a statement. "They will fly home aboard a Dragon spacecraft with two other crew members assigned to the agency's SpaceX Crew-9 mission."

That mission will launch no sooner than Sept. 24, NASA said. Four crew members were originally scheduled to be on board at launch, but two will now stay behind to make room for Wilmore and Williams' return trip.

As for Boeing's Starliner, NASA said it expects the uncrewed craft to leave the ISS in early September and "make a safe, controlled autonomous re-entry and landing."

The space agency said it'll share more information once plans have been finalized.

"Spaceflight is risky, even at its safest and most routine," NASA Administrator Bill Nelson said in the statement. "A test flight, by nature, is neither safe, nor routine. The decision to keep Butch and Suni aboard the International Space Station and bring Boeing's Starliner home uncrewed is the result of our commitment to safety: our core value and our North Star."

NASA and Boeing have "completed a tremendous amount of testing and analysis, and this flight test is providing critical information on Starliner's performance in space," Steve Stich, manager of NASA's Commercial Crew Program, said in the statement. "Starliner is a very capable spacecraft and, ultimately, this comes down to needing a higher level of certainty to perform a crewed return ... Our efforts will help prepare for the uncrewed return and will greatly benefit future corrective actions for the spacecraft."

What are the astronauts saying?

The astronauts don't seem to be panicking.

"We are having a great time here on ISS," Williams said in a news conference held from orbit in July. "I'm not complaining. Butch isn't complaining that we're up here for a couple of extra weeks."

And despite the Starliner problems, Wilmore seems positive about the craft.

"The spacecraft performed unbelievably well," he said, although noting that the thruster problems of the second day were obvious. "You could tell the thrust control, the capability was degraded," he said.

On Saturday, Norman Knight, the chief of NASA's flight director office, said he'd spoken with the two astronauts about the decision to return them on the SpaceX Crew-9 Dragon early next year, The New York Times reported.

"They support the agency's decision fully," Knight said, according to the Times, "and they're ready to continue this mission onboard ISS."

CNET's Edward Moyer contributed to this report.