Question about co-op

[Tacky]

Can people join your single player session at any time, or do they have to be invited? Also, let's say you invite a friend in for the last mission of SP. They join, and beat the game with you. Will that unlock all of the other SP missions prior to the one they played with you?

[King of the Flank]

First off I think you have to play your mission on Live and then that alowes other people on your friends list to jump in.

I don't think you have to invite them although I assume there will be an option to have it closed to people unless sent a request. Also I don't think you can unlock missions just by showing up at the end but who knows.

Not like it really madders though cuz I will play through the game rather quickly

[Trueskill]

Can people join your single player session at any time, or do they have to be invited? Also, let's say you invite a friend in for the last mission of SP. They join, and beat the game with you. Will that unlock all of the other SP missions prior to the one they played with you?
why in the world di u think we know?

[NP Silence]

I think that your always joinable....but you can probably decide not to be...and for the ulcoking thing i doubt it they pry beat the game though just will have to replay it all to get the acts completed

[The New Black]

You start a single player game, you call up your friends list and invite someone in. He takes on the role of Dom. While doing so, you can both complete the entire game, AND you both unlock achievements!.