Who do you think the other three are? If we're going with people who're on the same level as Observant...

[ There's a couple of people who come to mind, but the more she thinks about everyone's secrets, it's not as clear. Her and Terumi for being unabashedly here for things like what happened to Meteoric, Archer for... a lot of reasons, and his secret helps with that, especially since it matches Kimblee's nicely. Tarrlok? Kirei? ]

...there's a lot of choices, huh?