The voice in my head keeps joking that tonight's session is rated 'L' for 'Lethal.' Which means that there is a large fight planned for tonight's session where, if the dice go poorly, it could end up with a PC down and dead. It's not something I generally like to start a series of adventures off with, but with the story around what is going on - something I would be remiss if I gave the players no warning about until later on - it's just going to happen.
Maybe it won't. The players could always choose to just ignore the hook and continue on their merry way. I just don't think they will.
With all that said, how do you handle situations in which you feel the chance of a PC death is high? Do you forewarn your players (I do, if you didn't catch on.) Do you expect them to figure it out? Do you just treat it like a normal session until things start to go pear shaped?