It looks like Microsoft is running a special one-day-only promotion on Blacklight for the PC. Here is the link to the game. You can use a credit card or Microsoft points to purchase. It is downloadable through Games for Windows.
http://www.gamesforwindows.com/en-US/dailydeal/day4/
http://www.gamesforwindows.com/en-US/dailydeal/day4/