What do ‘it’ ‘on’ ‘off’ mean in “it’ll be on with the old Invisibility Cloak and off to find out what he’s –“?

Question

I have trouble understanding the bold part.Harry has a magical map by which he can see where others are. He is looking at the map and paying attention to his enemy schoolboy, Malfoy.>”Well, I’m keeping an eye on him (Malfoy) from now on,” he said firmly. “And the moment I see him lurking somewhere with Crabbe and Goyle keeping watch outside, **it’ll be on with the old Invisibility Cloak and off to find out what he’s――**“ He broke off as Neville entered the dormitory. (*Harry Potter and the Half-Blood Prince (6)* [US Version p.388])If I’m not much mistaken, the general meaning is “I’ll put on the old Invisibility Cloak and depart with haste to find out what he’s up to.” However, I can’t grab the make of the sentence. The problem is ‘it’ on the top of the sentence and ‘on’ and ‘off’. I thought ‘it’ meant Harry’s plan to detect Malfoy’s conspiracy at first, but in that case, I guess ‘off’ means ‘cancel’ or something. I feel it doesn’t make sense. I’m completely confused.What do ‘it’, ‘on’ and ‘off’ mean?

Answer 1

So, this is some colloquialism at work here and doesn't translate perfectly into the rules of English. I'm going to try my best to explain this. It's like hearing someone say "I'm tossing on the hat and getting to work". Harry is saying that he's putting on the cloak and (setting or going) off to find out what Malfoy is doing.

It's a little bit of word play on Rowling's part. She abbreviates the "off to find" from "going off to find", which might be the word you're missing.

The word "It'll" is sort of used in terms of "I will be" and "This situation is going to to be".

Basically the sentence is saying "It's time to put on the cloak and go and find out what Malfoy is doing". It's just more fun saying "On with the cloak, off to find out".

I hope that helps.