In it, you play as a race car driver who gets himself involved in the Paris resistance during WWII. In fact, your character is actually based on a real person: William Grover-Williams, a British race car driver living in France who was recruited by the SOE to lead part of The French Resistance.
As a result, you won't just be doing plenty of killin' and sneakin' around, you'll also do a bit of drivin', which the Pandemic guys illustrated by showing us the not-so-leisurely drive you take to Paris at the beginning of the game.
But even with this, and the game's open world Parisian setting, the game doesn't look as much like it's Mercenaries-esque as much as it does Assassin's Creed-ish. That's because your character isn't just good at drivin', sneakin', and shootin', he's also freakishly good at climbin'. You can climb any surface, so long as there's something for you to grab on to. And there's plenty to grab onto in Paris.