A masterpiece of storytelling. It does everything this era does best and cranks it up to 100.

It takes the concept of the Sensorites, where a non-hostile species takes center stage, but adds a moral conundrum by making this species immortal and unkillable.

This opens up so many venues and questions, and they all get asked throughout.  What does a lack of pain mean? Can love exist without loss? Is pain the price for progress?

As the party interacts with the species, they learn. However, they are careless with what they teach, which leads the species to wrong, but understandable conclusions. They have created their own enemy, but even that title might be too rough for a species that does not even have a concept for evil.

It just takes what we take for granted, and makes you consider on a base level if those assumptions are truly natural. The contrast the classic party brings to the table works wonders here. They don’t act differently from any other stories, but they just have such a low margin of comparison that it spirals out of control.

It is a masterwork. It leaves its ending a bit open, like usually happens, but that only plays to its strength. We don’t know what will happen, and we might not even be able to conceive it. All we can do is hope, and take a long hard look in the mirror.