Valve has acquired Turtle Rock Studios, the developer currently working on the ace-looking, Source-powered zombie shooter Left 4 Dead.
It means that Left 4 Dead, due for release this year, becomes a wholly owned Valve property.
"Left 4 Dead fills a long-standing demand gamers have had for a co-op first-person action experience, and it will also help Valve's expansion into the console market," added Doug Lombardi, Valve's VP of marketing.
Left 4 Dead was originally announced in November 2006 and finds a small band of humans (the Survivors) battling zombie hordes and nasty mutated beings - collectively known as the Infected - which have overrun the game's urban battlegrounds. Players will be able to play as both the Survivors and the Infected.
More on the game here.