Lena and Martin announce to the kids that Lisa Apple's baby, Annie, is their half-sister, and Martin is surprised when they aren't interested in meeting her. Lena feels the burden of being stuck in the middle between Martin and Lisa but still offers to help bring both families together. Meanwhile, Mason overhears Lena and Martin's conversation about Lisa's financial difficulties and decides to start a fundraising campaign to help. Elsewhere, Lena feels a bit of empty nest syndrome when she attends Mae's college fair at school.
