who are some top secret brilliant scientists

Hard to say if they're top secret.

I can't remember names but here's two interesting cases, the first has to do with anti-gravity research, a brilliant scientist... a woman, making progress, had a breakthrough.

VANISHED.

But rumour had it she wasn't killed or whatever, they took her in and kept going, she vanished down the rabbit hole and went to work for the man.

She was Asian if I recall correctly, I'm sure a brief search would turn up her name.

The second case was a couple back in the 70s I think, oceanic scientists, I don't recall as many details as the first example but I do know they were working on a project codenamed Neptune.

It had to do with communicating with dolphins, translating basically... they do were reported to be on the verge of a massive breakthrough and *poof* down the rabbithole they went.

I guess that really didn't help you OP, but thanks for reminding me about those 2 cases, I might read up on them again for nostalgia value.