1) Thomas is immune to a disease that has killed everyone else in the world over the past year. He lives alone, scavenging for food and supplies.
2) One day, Thomas sees a light turn on in a house as he walks by, indicating he may not be alone after all.
3) Though lonely, Thomas continues surviving by searching empty homes, collecting what he needs. He wonders why he is immune and what his purpose is, with no one left but himself on Earth.