Mel gets annoyed when Lucy keeps calling Sophie and Brian 'mum and dad'. She decides to show Josh and Lucy a box of their real parents' old possessions - but gets really upset when she discovers that one of her real mum's old lipsticks has gone missing. It turns out that Lucy swapped the lipstick for half a dictionary - but only because Mel had never told her how precious it was. Josh tries to fool Brian and Sophie about his bad school grades, claiming that the grades run from 'A' for 'awful' all the way up to 'F' for 'fantastic'. As a result they think Josh has done very well, but are really disappointed by Lucy's twelve 'A's. But when the truth comes out about Josh's poor results, Lucy offers to help Josh with his exam re-sits if Josh helps Lucy get the lipstick back. Meanwhile, Brian tries to build a high-powered vacuum cleaner based on Valuxian technology - and struggles with his strange allergy to ice-cream.