The episode begins with images from the Battle of Richmond on March 20, 1965 with a reporter Gideon Spilett pausing on the outskirts to write down his thoughts. Nearby, Jack Pencroft looks to escort black slaves away from the conflict but is captured along with his wife Joanna and son Herbert. Back on the battlefield, Captain Harding, who is mourning the death of his brother, along with aide de camp Neb are captured by Confederate soldiers.
Jack looks on helplessly as Confederates burn his boat before escorting him off to jail along with Harding and his aide. Meanwhile, Spilett decides to take a closer look at the helium balloon the Confederates are supposed to own. However, as he draws what the balloon looks like, he is confronted and arrested by soldiers on the suspicion that he may be a spy.
After the six introduce each other, they note that they are looking at being executed by a firing squad and quickly manage to escape from their cell. Jack heads in the wrong direction and a battle quickly erupts. Jack want to escape in a nearby wagon but Harding declares that the balloon is the only way to escape. The group makes it way to the balloon until only Jack is left to fend off the pressing Confederate soldiers. Just as the balloon starts to float away, Jack runs desperately across the grounds and grabs onto one of the mooring lines in the nick of time. After a few tense moments, he is pulled onboard as the balloon sails away.
After a short period, the group realizes there is a hole in the balloon that needs to be repaired urgently. Finding a crude needle, Jack climbs up and manages to effect repair to keep the balloon aloft. However, the group has no way of steering the balloon and they find themselves drifting above the clouds towards an unknown destination.
With no control over their fate, tempers quickly become frayed as several options are tried to lower the balloon's altitude to no avail. Spilett notes in his journal that they are traveling west according to Pencroft and they are scared to sleep for even a tiny amount of time.
The focus shifts to a solitary figure on an island who seems to spot the approaching balloon. Back on the balloon, Harding notes that they have been blown across the country and now appear to be above the Pacific Ocean. Neb calls out that he sees what looks to be land directly in front of them. On the island, the figure aims what looks to be a sniper rifle in the balloon's direction and shoots a hole in the balloon.
When Harding and the others note the hole, they immediately start dumping weight and climb into the rigging to cut loose the basket in an attempt to stay aloft. Still sinking too fast, Harding jumps off the rigging into the ocean to the dismay of Neb. The remaining individuals hang on as long as they can until, one by one, they drop into the ocean near the island.
Shortly thereafter, they regroup on the beach except for Harding, who is believed to have drowned by everybody except for Neb. As for Harding, his is out in the ocean and slowly sinks under the surface to his apparent death.
With night approaching, the castaways set up a shelter on the beach and gather mussels to eat. Afterwards, as they settle in to sleep for the night, they are unaware they are being spied by an unknown person under the ocean.
The next days, the castaways awake to the sound of Neb down by the water calling out for Harding. Herbert offers to help Neb with his search but is rebuffed. However, Neb does relate that he has found a source of water to the relief of everyone. Shortly afterwards, the castaways make plans to find food and shelter inland with Neb and Herbert setting out. Herbert stumbles over a rock and finds his leg wedged tight under a large beach rock with the tide coming in.
Neb searches a nearby cave desperately for a piece of wood or something similar to free Herbert until he finds just such a piece that looks to placed between his feet by unseen hands. Neb frees Herbert and the two head into the cave to find a fire that wasn't there previously.