After Penelope's first season ends without any suitors, she and Colin make a pact.
If they're both unmarried when she turns 29, they'll get married to each other.
At first, Colin doesn't believe it'll happen because he thinks Penelope will be married long before then. And Penelope is almost hopeful that she won't.
But by the time Penelope is 27, he starts to come around to the idea of marrying her. So, who is this Mr. Anderson hanging around Penelope, now?
Meanwhile, Penelope is convinced that Colin doesn't remember the pact.