Matilda and the Ramsay Bunch are in sunny LA, the city that loves to party and having a summer to remember. To celebrate dad Gordon and mum Tana's 20th wedding anniversary Tilly is cooking a Mexican feast and the biggest cake she's ever made. To throw the ultimate surprise party for mum and dad, Tilly, Megan, Holly and Jack are going with a major Mexican theme - amazing costumes and a special guest appearance from a brilliant 13-year-old mariachi singer. On the menu is Gordon and Tana's favourite Mexican dish, enchiladas, as well as a zingy prickly pear salad. And to top off the meal is Tilly's huge 20-layer rainbow tower cake, one layer for each year mum and dad have been married. But with dad determined to find out what's on Tilly's secret menu, she's going to have to be extra secretive to make sure the surprise isn't ruined!