It's sense-of-wonder SF, introducing our first life outside the solar system. What's more, the strip knows what a big deal this is. Mysterious things arrive and it takes us over three months of the weekly magazine to see one of their faces. (I love that build-up.) Dan and Digby have to get in a submarine and dive down 8.5 km to the floor of the Tuscarora Deep, once thought to be the world's deepest sea trench.
This is the kind of thing this series excels at. I wouldn't call it thrilling, despite a giant squid and a submarine-eating monster fish, but it's intriguing and intelligent. I love the weird space stuff our heroes see when travelling faster than light. They catch up with Earth transmissions from almost three years ago (the Red Moon), which is straightforward science but still fun to see the strip playing with. There are... ghosts? Phantoms? Gelatinous things. Deep space beyond the solar system can be reminiscent of the ocean deeps.
As for the Crypts, there are things their eyes can't see, while you need to get clever with tape recorders even to communicate with them. They're also a little bit beautiful, despite those dinosaur beaks. Female faces. Male bodies. Referred to with male pronouns.
Dan's excited about exploring a new world. "I'm due for some very queer experiences!"
The strip's only problem is Flamer. The child heroes worked in Prisoners of Space, but here there's no plot excuse for Flamer's presence. He even goes with Dan beyond the solar system! Sir Hubert says no, but they convince him. Good grief. You'll want to headbutt walls, although Lero's intervention sort of semi-justifies it.
There's someone a lot like Captain Nemo, with a beard and a submarine. Incidentally, the strip's 1955 idea of 21st century marine technology is surprisingly accurate. You'll read it today and usually be thinking, "Yup, we do that." Mind you, today's Japanese fishermen use boats a bit more modern than the "Nippon" (sic) ones we see here.
At one point, the strip turns into a mock newspaper. This series liked doing that occasionally.
This one's pretty cool. Dan's his usual daredevil self, unsurprisingly. "Tails! I win!" (...for a very Dan definition of "win".) Even the art's different, with a strong use of conventional comics inking before the colours got painted in. The strip's aware that it's crossing further into science fantasy with faster-than-light travel, so they make a big deal of it with smugly wrong Earth boffins and Crypt technology that leaves ours in the dust. "It's shattering, Dan. It means that the Hemming modification to the relativity theory will have to be completely revised!"
There's even a cliffhanger ending. I'm fond of this one.