Ruby's teacher asks Ruby and Yasmin to look after a new girl at school. Her name is Lauren, and it is not long before she manages to upset the uneasy equilibrium between the two best friends. Ruby resents the way Yasmin often waltzes off, leaving her to entertain the extremely shy Lauren.

Meanwhile, back home Ruby is under pressure to accept Tiffany as brother Joe's girlfriend, not least because Holly seems to have got together with another boy. However, St Valentine's promises some fun events and an opportunity for a little Valentine card devilment to relieve Ruby from all this relationship stress and get back at Yasmin. Of course, things do not go exactly according to plan and Ruby soon finds herself in rather hot water . . .