The fifth time is apparently sometimes the charm. Or else this was an anomoly.

I've written a little Don/Charlie fic, rated NP for no porn. Scrape (10k).

Charlie was lying on the couch with the latest issue of Discrete Applied Mathematics; when he looked up, it was to try running a cycle of Cechlárová's algorithm for testing eigenvectors in his head. Sight cut in before sound, so for a few seconds he was processing the algorithm and watching Don walk through the noon-bright living room, waving his hands expressively as he spoke.