If you still haven't taken a look at HITMAN [Steam], now is certainly the time to do so. You can grab it from now until January 5th and get a permanent copy of the first episode set in Paris.
To be perfectly clear, Paris really is yours to keep! From the announcement:
Once you’ve downloaded it, Paris is yours to keep permanently.
Included in the free pack is: the first major story mission from the game, ‘Showstopper’, plus all of the Escalation Contracts released for Paris, the ‘Holiday Hoarders’ mission plus the Paris Challenge Packs and achievements.
If you like it, you can of course contribute to future HITMAN games and future ports from Feral Interactive by buying the rest of the episodes. I think it's well worth it, such a great game! Of course, progress made will carry over if you do decide to upgrade to the paid version.
See the announcement here.