Devika Cullen and Rick Attah descend from the Lovell Platform in the Genetrix probe to the surface of Venus. They stop a few dozen kilometres above the surface and wait for the atmospheric sifters to collect data on the atmosphere. All of a sudden, the probe pitches and begins to fall. There is a power drain to the systems, and they can't raise the platform on the comms. There is a banging on the cockpit door, and it opens to reveal the Twelfth Doctor and Clara. The Doctor tells them to get in the TARDIS, but Devika says they can't leave the valuable data and equipment on the Genetrix.
As the heat and pressure in the cabin rises, the Doctor spurs the crew into action. The hull starts to buckle and gas leaks in. Clara calls the Doctor down to the lower deck, and Devika and Rick follow. They find her pointing the sonic at a gaseous humanoid lifeform, which the Doctor identifies as native to Venus and nicknames "Wispy". As it sprays acid on the control banks, the Doctor asks what those controls do. Rick says they control the atmospheric sifters. The Doctor realises the sifters are sucking up the gas creatures. Clara and Rick distract Wispy so the Doctor can get to the controls and purge the sifters. The heat and pressure continue to rise. Clara throws the Doctor the sonic and just as Wispy is about to attack him, he purges the sifters.
Wispy dissipates, but the Genetrix is still being torn apart. Suddenly, it stabilises, and the air returns to normal. Clara and Devika watch as dozens of the gas creatures lift the probe up through the atmosphere. Back on Lovell Platform, the Doctor, Clara, Devika and Rick watch the sun set on Venus.
- Lovell Platform and the Genetrix are projects of the International Aeronautical Space Agency, or IASA.
- The Genetrix's ballon is made of dynastream.
- Rick sings "Magic Carpet Ride" by Steppenwolf. Devika suggests he try The Beatles next.
- Clara asked the Doctor to show her a Venusian sunset, which only happens once every 116.75 Earth days.
- Eighth century alchemists called sulphuric acid "oil of vitriol".
- The gaseous Wispies are made up carbon dioxide, nitrogen, and sulphuric acid.
- This short story accompanied a chapter entitled "Alien Life and Other Worlds".