From the publisher:
The cousins' parents are coming home! Of course Lily, Tess, and Rosie are looking forward to seeing their parents, but they're also sad about leaving their cozy attic room in Aunt Lucy's little blue house on Cobble Street -- and each other. So they plan a summer party to welcome their parents back and to cheer themselves up. But it's Aunt Lucy's boyfriend, Michael, whose wonderful surprise makes the party really special.