The idea that an advanced alien species would judge humanity harshly is one of the oldest sci-fi tropes. From Arthur C. Clarke’s Childhood’s End to several iterations of Star Trek — including the inaugural episode of The Next Generation — pondering judgment from outer space is the source of one of the genre’s most important questions.

Our species might be smart enough to get into space, but will we be good enough for the aliens we find there?

In the 1951 classic The Day the Earth Stood Still, a flying saucer comes to us and produces a man who, by all accounts, appears human. Klaatu, a kindly, philosophical alien who simply wants humanity to calm down and stop destroying each other, was played by Michael Rennie, and it’s hard for sci-fi aficionados to picture another actor in the role. But we should, because Keanu Reeves’ take on the character in the 2008 remake has an intriguing dark edge. Reeves gave the world a great take on an old character, making the story’s concept more relatable.

What makes the Keanu Reeves version of Klaatu more exciting than Michael Rennie’s isn’t just the fact that he’s played by Reeves, who in 2008 was just five years removed from the Matrix trilogy. Instead, this version of The Day the Earth Stood Still is worth rewatching because it’s actually a fairly faithful remake with only one major change: Klaatu isn’t fond of humans, and at first he has no desire to spare the human race.

Even after a fellow undercover alien, Mr. Wu (James Hong), tries to tell Klaatu that humans aren’t all that bad, he remains unconvinced. Only after hanging out with idealistic astrobiologist Helen Benson (Jennifer Connelly) and kooky professor Karl Barnhardt (John Cleese) does Klaatu come to doubt his plan of saving all the animals and letting the humans bite it. Maybe humanity is worth it after all.

But the ending inverts the original film. Although it takes most of the movie for Klaatu to be convinced, the final moments find him deactivating much of Earth’s technology. Thematically, this works better on paper than the original film, since humanity’s quasi-punishment for the destruction it’s wrought is doled out at the end. So the moment when everything stands still happens at the end, making Klaatu’s warnings seem more poignant. This is a wake-up call for humanity: everything stops working, and won’t start again until our species sorts itself out.

Keanu Reeves ponders his orb. 20TH CENTURY FOX

In the classic film, the mystery of everything standing still happens at the beginning, which packs much of the philosophical message into the early scenes. As great as the original Day the Earth Stood Still is, it almost overplays its hand early in the narrative. This isn’t to say the Keanu version is better, but from the perspective of cinematic tension, the 2008 version seems more aware of its power.

For hardcore sci-fi fans, it would be a fun exercise to watch these two movies back-to-back. But for more casual fans, the real reason to watch this version is to see Keanu Reeves playing an alien. It’s not exactly a dead-serious performance, nor is Reeves going for any kind of otherworldly camp. He’s actually trying to convey the idea that he is an alien who has taken human form, another trope we’ve seen a billion times. And yet, in the hands of one of our greatest genre actors, Reeves makes that idea feel refreshingly, and startlingly, brand new.