Despite the trailer leaning into the sci-fi horror vibe, Netflix's Stowaway turned out to be a heart-wrenching thriller examining just how far someone will go to save a life. But, I'm not going to lie: the entire premise of Stowaway is bleak, and the ambiguous ending leaves you wanting more.
Shortly after takeoff, the crew of a two-year mission to Mars — captain Marina Barnett (Toni Collette), biologist David Kim (Daniel Dae Kim), and medical researcher Zoe Levenson (Anna Kendrick) — discover they've been joined by an accidental stowaway, launch support engineer Michael Adams (Shamier Anderson). Unsure of how he ended up unconscious on the ship and wanting to go home, Michael reveals that his last memories are of preparing the Hyperion ship for takeoff.
Soon the crew discovers that Michael's fall through the ceiling inadvertently damaged the CDRA, which scrubs the ship of carbon dioxide beyond repair. This means that they are running out of oxygen. They also learn that the ship does not have enough fuel to get them back to Earth, thanks to the added weight of Michael during takeoff.
Working through every option, Hyperion decides the best way to salvage the mission and survive is through the death of Michael. David explains the situation to Michael, offering him a lethal injection so that Michael can be the one to decide when and how his death happens. At the last minute, Zoe convinces Michael not to commit suicide and tells the rest of the crew that they have to attempt a risky mission to retrieve liquid oxygen from the launch vehicle.
Just as David and Zoe begin to fill up their oxygen tanks, a solar flare forces them to return to the ship and abandon one of the tanks. Zoe also manages to lose their full one in the process, dooming an additional crew member, as there is now only enough oxygen for two people on the ship. Despite the dangers of radiation from the solar storm, Zoe volunteers to retrieve the other tank so that the rest of the group can survive. After successfully retrieving the tank, Zoe sits atop the ship watching the solar storm as the effects of the solar radiation begin to take hold.
Despite not actually showing her death, Stowaway circles back to Zoe's monologue about why she joined the mission and how she was looking for something that "gives her life meaning beyond anything she could imagine." Sacrificing her life for the lives of others certainly accomplishes that goal. As for the fate of the rest of the crew, Kendrick previously told Collider that she "assumed" they survived and that "I think some of the crew makes it to Mars!" Kim also added that "thanks to the actions of some of our crew, the rest of the crew makes it."
Stowaway is currently streaming on Netflix.