A mystery illness leaves Topaz the kangaroo (pictured) without a hop - and the vets scratching their heads.When Topaz is taken for treatment, rumours begin to spread around the Zoo that it could be ‘Uncle Nigel's Hoppitystophop' - a horrible condition that causes kangaroos to lose their ability top hop.Jealous of all the attention on Topaz, hapless gorilla and self-appointed leader of the zoo Jürgen conjures up an illness in need of treatment of his own. Diagnosed by fellow gorilla Geoffrey as "attention-seeker-itis" will he and Topaz ever recover?