When Penny and Bernadette got to San Diego for a pharmaceutical sales convention, Howard is left in charge of the kids. But when Sheldon finds a book on experimenting with children, the guys and Amy make a day of it.
When Phil thinks Luke is giving him the cold shoulder, Andy becomes Phil's new right-hand man; Jay is put in a tough spot when it is suspected that Joe is allergic to Stella; Mitchell does some freelance legal work at Jay's company.
Lyndsey and Alan try to add a little excitement to their love life.
Mac begins to control the new incarnation of "News Night"; Jim takes the fall for Maggie's miscue; Charlie forbids Reese from secret meetings with Will.
Marshall goes to his father's grave for New Year's Day tailgating; Barney and Ted open a bar; Robin fills in for a news anchor.