"The Staircase Implementation" starts with Leonard and Sheldonfighting over the thermostat, as expected from any great episode of TBBT. Penny (Kaley Cuoco) calls him crazy for putting up with Sheldon, ...

Leonard recounts the tale of how he ended up living with Sheldon, despite lots of warning signs that this may not be a great idea. Also, the mystery of the broken elevator is finally addressed.