Tully and Kate meet as young girls on Firefly Lane and become inseparable best friends throughout 30 years of ups and downs.
When unlikely duo Tully (Katherine Heigl) and Kate (Sarah Chalke) meet at age 14, they couldn't be more different. Tully is the brash and bold girl you can't ignore, while Kate is the mousy shy girl you never notice. But when a tragedy brings them together, they are bonded for life -- forever inseparable best friends. Together they experience 30 years of ups and downs -- triumphs and disappointments, heartbreak and joy, and a love triangle that strains their friendship. One goes on to fabulous wealth and fame, the other chooses marriage and motherhood -- but through the decades, their bond remains -- until it faces the ultimate test.