This program explores further the idea that everything is made of particles. It looks at the difference between atoms and molecules, the difference between elements, compounds and mixtures,how an element like lead can exist in various forms (as an element or in compounds), and how this can affect its properties (eg. how poisonous it is), why a substance may dissolve in one liquid but not another. Features a visit to a scientific testing laboratory and discussions with a forensic scientist discussing arsenic and whether it may have contributed to the death of Phar Lap. A case study looks at a mysterious illness in a family pet, which is traced through scientific analysis to the presence of lead in the backyard soil.