It's titled Chiroptophobia and is a lively and creepy adventure with Tosh and Ianto - and batty things. Seriously, it says so in the summary!
Summary: People are going missing at the Gregory White Memorial Library. Ianto and Tosh investigate - and run into a whole heap of trouble (and batty things).
Come on, give it a try, get creeped out by batty things!
Ooops, forgot the link! It's right here: http://tw-classic-bb.livejournal.com/7078.html