It's Pam's first day back to work from maternity leave. Pam already misses baby C.C.
Andy tries to convince Michael to invite Erin to lunch for Secretary's Day. Michael is very hesitant but caves in, even taking Erin to her favorite restaurant, Hayworth's. The ride over is a bit awkward -- Erin tries to stir up conversation when all Michael really wants to do is listen to his book on tape.
Erin continues to try to coax Michael into a conversation and he opens up when she brings up Andy. Erin wants to know what Andy was like before she met him. Michael tells her Andy dated Angela and the two were even engaged. This is the first time Erin's heard about Andy and Angela.
Erin is extremely hurt after hearing about Andy's past with Angela. Back at the office, Andy is clueless as to why Erin's acting so cold towards him. Erin even surprises Oscar by snapping at him.
Kevin is feeling left out after discovering he's part of a joke circling around the office comparing him to the Cookie Monster. At Erin's Secretary's Day party, Kevin watches on as different co-workers do their best impressions of him. Gabe tries to step in to defend Kevin, but is ignored.
Andy gives a speech about how great Angela is for throwing Erin's party. Erin just stews in the background. Andy takes out the guitar and prepares to dedicate a song to Erin called, "Secretary of Love," but before he can get started, Erin throws a slice of cake, nailing him the face. Erin tells Andy that Michael spilled the beans about him and Angela.
After Pam does her own impression of Kevin as Cookie Monster, Gabe steps in and suspends her for two days without pay. He also suspends Jim and Dwight for talking back to him. Gabe later finds out his authority level doesn't allow him to grant suspensions.
Andy divulges to Erin that he and Angela went out for about a year. Erin isn't over the fact that Andy kept that from her and tells him she needs to break up with him. She later confides in Michael and he tells her Angela doesn't even hold a candle to Erin, making her laugh through her tears.
Gabe tries to win back the office by offering to buy them all coffee. They all refuse to accept. Then Gabe tries his own Kevin as the Cookie Monster impression, but even that doesn't garner a reaction. Kevin interrupts and does his own impression of Gabe, which everybody laughs at. Everyone joins in with their own Gabe impressions.