If anyone is yet to play the first season of HITMAN, they really need to do so.
It's a ridiculous amount of content and variations, enough to keep you busy for quite some time.
Since I assume this is a key for HITMAN, after activating it, instead of downloading it, be sure to go to Steam, and install the free HITMAN 2 Starter Pack instead:
When you launch it, it will detect you own the first season, and download the maps.
That way, you will play all of the first season's content in HITMAN 2 (with improvements), plus the prologue/intro of the second season/game, and your stats and unlocks will be kept for the future, in case you are interested in buying the second season/game (or the upcoming third).