In order to establish the past of Cecil Sloane (who I'm pretty sure the game calls Cedric Slone), you need to send Wayne De Spiritwhistle and Patrick Bannon through the rooms in the 1st segment in a specific order.
First you send the pair to The Costume Room (button with the hanger)
Next you send the two to The Workshop (button with the saw)
Lastly you send the duo over to The Prop Store (button with the dumbbell)
After doing this, the achievement should unlock by the first break.
Note that this is the path I took. Judging by the end screen, the only thing that matters might be the last step.