It’s amazing that the commercial towing crew of the Nostromo explored an alien planet without any of the precautions, which would be taken in visiting a contagious ward at a hospital. How did they expect that the life on this planet would be friendly and compatible with ours?
Three crew members, Dallas, Kane and Lambert discover that the signal which brought them here, is coming from a wrecked alien spaceship. Upon further investigation, Kane stumbles upon a hatchery for aliens. He sticks his face up closer for a look and one of them attach itself to him. Amazing sense of precaution demonstrated here.
When Lambert and Dallas rush him back to the ship, Ash, the science officer, overrides Ripley’s authority and allows them to board, violating the quarantine protocol. It was astounding that they threw all caution to the wind in regards to this dangerous contagion. They even allow Kane to eat dinner in the general chow hall after his miraculous recovery. That in itself was mind boggling. It was no less of a surprise that an alien exploded from within his stomach and killed him at the dinner table.
It is soon discovered that Ash is, in fact, a robot, who is working under the direct command of the company to bring back the alien as a first priority with no regards to the crew. He supposes that it will be used for warfare, since it is albeit indestructible.
One by one the crew members are killed by the beast, which continues to grow in size, until only Ripley remains. She decides to destroy the spacecraft and escape on the shuttle so that the alien will be destroyed. It is most terrifying to discover that it is actually on board the small craft with her. I don’t think that I could have remained as calm and decisive as she did and solve the problem by flushing it out of the craft and into space.
The alien could represent any problem, when if ignored, grows into an unmanageable situation and can literally destroy all those around it.