Big and Small want to prove whether the Gwelf is real, as Small thinks, or just the fictional character that Big believes. They set up a machine in the garden to record the Gwelf when or if he comes into their garden that night. Ruby, however, secretly uses the machine to record her latest song. Just as the song ends, Big and Small hear Ruby in the garden. She panics and accidentally causes the machine to malfunction. Her song is played backwards and sounds really weird. But Ruby denies touching the machine, which causes Big and Small to think that it was the Gwelf who had been in the garden.
Big and Small prepare their Gwelf-detecting equipment and go marching off. Ruby is worried about her friends going into the Mysterious Woods at night and she tells them the truth. Small is shocked that Ruby would tell a fib about seeing a Gwelf. Ruby apologises but says if they will listen to her song properly they will be more understanding. Big mends the machine and Ruby's song is played: it's a jolly number about how much she likes living with Big and Small in the house and the fun they all have together. Small forgives Ruby for fibbing and they are all friends again.