The Bannerworths have finally decided to leave the hall instead of holding another drawn-out meeting about it, the Admiral having convinced them it was a good idea way back in Chapter I'm-not-looking-up-a-link-right-now.
Henry says to the Admiral: "here we are, trusting implicitly to you"; and for some reason the phrasing of that line just strikes me as funny. I know the awkwardness is just classic JMR dialogue, but it sort of has the feel of overeagerness, a shifty-eyed "of course I trust you; I haven't left some kind of sinister surprise for you when we leave."
Or maybe it's just me. It'd never happen, in any case.
The Admiral reassures Henry that he can defend himself against the vampire, and reassures Flora that she will at long last be away from her attacker. The Bannerworths (and Jack, who is accompanying them as comic relief) say farewell to the Admiral (and Dr. Chillingworth).
With the separation of Jack from the Admiral, JMR seems to be trying out a new running gag wherein Jack says something in sailor slang and the others stare blankly. Actually I can't tell if it's a running gag yet and not just a one-off, but from the way it was abruptly shoehorned into the beginning of the chapter ("Oh, it's a seaman's report. I know what he means; it's quicker and plainer than the land lingo, to my ears, and Jack can't talk any other, you see," says the Admiral) and then appears towards the end, that's what it feels like.
It's not funny for the same reason that a lot of JMR's attempts at humor aren't funny (see also: the last chapter): because they don't involve interaction. The Admiral and Jack are funny when they interact with each other. The Admiral is funny when he interacts with other people. Jack is a little too forced for me to find him funny most of the time, but he's funny when there's an actual interaction, and not just him saying something that's supposed to be funny and no one else really understanding it.
At any rate, the Bannerworths reach their destination uneventfully, and we've got to wait until the next Sunday post (which shall hopefully not be on Wednesday again) to find out what happens after the big cliffhanger at the end of this chapter: why can't the Bannerworths enter the garden yet????