Hello Guys and Gals!
Here is a video guide made by me, for the "Plan B" Achievement.
Now, for anyone who has trouble getting Redmond to appear at the party (Like Myself), what you have to do is replay Volume 3, Chapter 3 (Chips Misstep Part 2) and at the end when you are speaking with Agent Ikea, you have to press the "X" Button all the way through (If Chip is alive, If chip is dead by you stealing the Hard Drive, you will need to press the "B" Button at the very end of the convo to distract the agent with Pavonis Hard Drive) and you will know if you have been successful when Redmond says "You did well in there, that will get her off our trail for a bit"
Its at the start of the video anyway to show you what i mean.
Hope this helps!