It should be done with no space and an em-dash:
she remembered, with a shock, that Albus's own—
If em dashes aren't possible on ff.net, then use two hyphens in a row.
Honestly I don't think this is a case where making the audience work for it is really useful. The actual answer is revealed in the next chapter, so it's not like you're keeping it a secret for any length of time, but most people probably won't connect Albus' "my own father was in Azkaban statement" with Minerva's truncated though. The people wanting to solve the mystery don't have much payoff, the people who assume it's writer-error will just be confused.
Honestly I think "Albus' own father --" would works better. There are places for clever, mysterious writing but this isn't it.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.