There was a tap on the dark window.
“It's Hedwig!” said Harry, hurrying to let her in. “She'll have Charlie's answer!”
The three of them put their heads together to read the note.
How are you? Thanks for the letter — I'd be glad to take the Norwegian Ridgeback, but it won't be easy getting him here. I think the best thing will be to send him over with some friends of mine who are coming to visit me next week. Trouble is, they mustn't be seen carrying an illegal dragon.
Could you get the Ridgeback up the tallest tower at midnight on Saturday? They can meet you there and take him away while it's still dark.
Send me an answer as soon as possible.
They looked at each other.
“We've got the invisibility cloak,” said Harry. “It shouldn't be too difficult - I think the cloaks big enough to cover two of us and Norbert.”
It was a mark of how bad the last week had been that the other two agreed with him. Anything to get rid of Norbert — and Malfoy.
I don't quite understand the last two sentences in bold above, especially the first one. The sentence seems to be saying: it was a mark that the other two agreed with him. But I don't get what it is trying to convey and what "a mark" really is? What's the correct way to understand them?
--Excerpted from Harry Potter.