The team find out how the discovery of germs made disinfectants a bestseller.

The team take on the challenges of the 1850s and 60s, a time when overcrowded and unsanitary living conditions had reached their peak, leading to unprecedented outbreaks of disease. 'Cure all' medicines that had promised to cure virtually everything were all the rage and the team make their own out of rhubarb, liquorice, soap and syrup. They also venture into the uncertain world of electrotherapy and find out how the discovery of germs made disinfectants a bestseller; but to make their own they need to extract carbolic acid from coal tar. Plus Tom attempts to emulate an ambitious Victorian publicity stunt by building his very own dog-powered mortar and pestle. But will it work?