Fantastic Four (1961 series) #22

While Johnny Storm annoys Ben Grimm, Reed Richards investigates how Sue Storm's invisibility power works because he suspects she can do more with it. And when Thing aims a fire extinguisher at Human Torch which splashes towards Sue instead she automatically defends herself by erecting an invisible forcefield shield. Reed surmises that the radiation he was examining her with must have triggered her new power. He gets Sue to create a stronger, thicker forcefield by concentrating on it which neither Ben's strength nor Johnny's flame can penetrate.

Their experiments are interrupted by the arrival of a cop who's come in answer to complaints that the Fantastic Four's private ICBM violates local zoning laws. Reed takes him away to show him his Civil Aviation Authority permit and the cop asks him for an autograph, for his partner of course. Meanwhile Thing answers multiple phone calls from citizens complaining about other stuff which he resolves by destroying the phones. Next a sculptor shows up with his lawyer to sue Torch because his latest piece melted when HT flew past his window. But suddenly the pair are lifted off their feet and zigzag down the corridor to the elevator. Frightened they exit and Johnny notices Sue standing nearby laughing.

She goes to the elevator door and returns appearing to carry something which turns out to be an invisible tea tray table which she then makes visible. She's now learned how to make other things invisible, but she can only make 1 thing invisible at a time, including herself. She practices on Thing.  Then Reed has to deal with 4 mature women protesting at the possible consequences of his dangerous experiments but they're frightened off by invisible Thing manipulating a collection of parts from Reed's robot experiments.

All these complaints convince Reed they need somewhere more private as a base. And he's just been sent a pamphlet advertising a deserted island for sale cheap off the New Jersey coast. So they hop into their amphibious U-Car (introduced in Annual #1) and head there to check it out. When they get there they discover that the island is surrounded by a high barrier reef but Torch melts a way through and soon they're exploring the creepy place.

Sue senses someone else on the island and they suddenly see their U-Car pulled underwater. HT flies to investigate but is smothered by the steam he causes. Mr Fantastic extends his elastic body to rescue him. Ben complains that now they're trapped on the island.

They see someone watching them who runs off and they give chase into a cavern. MrF reaches out his elastic arms but gets trapped (surely not!) by a falling 'handcuffs' of rock until Thing smashes them. Then the mystery man steps forward and it's Mole Man who 'welcomes' them to his kingdom Subterranea. He's backed by some of his small, pale-skinned Subterraneans. He 'confesses' that he lured them here with the complaints and the pamphlet, and then he pulls a lever which opens a chasm that they fall into ...

... and land on a circle of soft netting surrounded by a low wall which Ben immediately sets off to climb over until Reed stops him because the wall is radioactive and would kill him. He could tell because it glows (and because he's read the cover). Then they see MM leaning on it with minions peeking over. Moley explains that it's only radioactive on the inner surface. He also explains how he escaped the destruction of Monster Isle in #1 via his network of underground 'railways' that the Subterraneans constructed under his guidance. And since then they have placed huge hydraulic platforms under the largest cities on Earth. He intends to simultaneously pull them all quickly down underground which will cause all sides to assume they have been attacked by another and the result will be nuclear war after which he will be able to rule the surface world. And his hated enemies the FF will have to watch it all. (Bwah-ha-ha!)

A minion brings him a cushion with the trigger on. But Invisible Girl surrounds it with an invisible forcefield and Moley can't understand why he can't get to it. Choosing a moment when the villain has given up Reed gets Sue to switch the forcefield to surround the 4 which enables them to safely scramble over the wall. They have to fight through minions with medieval weapons but Torch flies to attack the main man who pulls a sash which causes a floor panel to open and suck Johnny down into a cell while extinguishing his flame. The panel closes and then Reed and Sue also fall through other panels. Another sash sends charging Thing down a hole ...

... where he finds himself sinking into a huge soft mass. His struggles to get out just cause him to sink further into it and he's in danger of suffocating in cotton. But he uses his brain and his hands to locate the pipework that's pumping the stuff in, and yanking that part of the wall out he finds a tunnel large enough for him to crawl through. Meanwhile Sue has ended up in a normal-looking living room but the furniture and decorations are all illusions. MM on screen tells her she has 30 seconds before a nerve gas canister will explode to kill her. But she uses her invisibility power in reverse to make what's hidden visible and spots an airlock which she uses just in time. Mr Fantastic is trapped in a room with non-porous walls he can't 'seep' through, and he gets nerve gas too. But he rolls himself into a ball which he then expands forcing the walls to crack and he's out into a room containing a bank of machinery which he starts to mess with. In Johnny's cell photoelectric cells detect whenever he tries to ignite a small flame and extinguish it. After that the room becomes freezing cold. But he breaks off an icicle and uses it to smash the photoelectric cells which allows him to flame on and melt his way out.

Thing is plowing through Subterraneans to get to Mole Man who turns all the lights out because his radar sense gives him the edge in the dark. He lures Ben over the edge of a vertical drop, but Mr Fantastic's arm stretches to catch him and allows Ben to climb to safety. MM lashes out with his staff but MrF's arm twitches aside, and then Thing is up and attacking again. The villain pulls another lever and a large boulder falls towards the 2 heroes, but Torch arrives to blast it and allows them to see their foe diving down a chute which takes him to his throne room and the control device.

Reed tells all his team they must leave quickly and he hasn't time to explain. They worry about the threatened cities but do what he says. They fight their way through more Subterraneans to where Sue has spotted the U-Car and escape in it. Moley reaches the control device and pushes the button ...

... and his island sinks into the ocean. Reed explains that a few pages back he rewired MM's machine so that the human cities were safe but the villain's scientific complex was flooded.