
I had meant to get started on this some days ago, since there have been a few significant updates of late.
Fist some totally obvious clues as to Tarquin's alignment:
755
756
757
But Elan steadfastly refuses to accept the truth.
758
DUN DUN DUNN: we finally see not only Haley's dad but we realize that Elan's dad was behind the capture of Haley's dad (of course many suspected that all along)

759
And he finally wises up. The title "Yes, Apparently" presumably refers to Haley's question in the second to last panel. Poor Elan. Tarquin really had to make it blatantly obvious for him though.

760
Climatic battle scene ahoy! On a rooftop no less. Somehow I doubt that Tarquin will be defeated here, since it's not time yet for a villainous defeat. Unless Vaarsuvius or someone else manages to pull a spoiler like with Kubota or something. I doubt it though: Tarquin is more important than that.