I had a look around but didn't really found one but are there actually some Grey Knight scenario's available that are playable in a single Session? I ask because I only have the basic Dark Heresy rulebook and now just bought Demon Hunter. My wife loves playing Space Marines (we already played a session of Deatchwatch and she was a Chaos Marine in Broken Chains) so I tought it would be fun for her to play a Grey Knight as well.

i know that in the back of deamon hunter there is one premade game example, but other than that i don't think theres any other ones,

but you could change any deathwatch mission to fit the grey knights, just add deamons instead of regular mobs!! sorry to not know of any out there.

Actually, I'd say keep the mobs, just make them demonic. 3-4 Grey Knights against a sea of lesser demons is suitably epic.