in the viselike grip of a raving lunatic

[frindle]

Hello. Would you please tell me what the underlined sentence means in this context below?
Does it mean he probably holds tight something not to slip on the bathroom floor?
Please help. Thank you.

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(In the story a boy try to break and enter Mr. X's apartment. Because he believes Mr. X is a killer or something. He wants to find positive proof there.)

"Call the police if I'm not back in 10 minutes."
"Are you serious? What if you wipe out in your socks on the bathroom floor up there, hit your head on the bathtub, and pass out, and then I call the police, and we have to explain what you were doing up there in the first place? We could go to jail!"
He stares at me. Then he bends down, takes off his socks, and tosses them.
"If I'm not back in 10 minutes, call the police because it means I have not slipped in the bathroom in my socks and I am most likely in he viselike grip of a raving lunatic. Okay?"

[SoothingDave]

No, it doesn't. It means that Mr. X, the suspected killer whose apartment he is breaking into is, in fact, a "raving lunatic" and is holding him tight.

[BobK]

It's quite an understandable misinterpretation though - by someone who looked up vicelike (sorry about the c, I just can't bring myself to spell it the other way), and was pointed by an unhelpful dictionary to the entry for vice. Plumbing tools would have been on frindle's mind.

b