The team try to demonstrate their aptitude for forensics. Meanwhile, commanding officer Dl Beach takes them on a murder-mystery weekend.

The Good Guys begin the next stage of their training, forensics. They are sent to the scene of a sweet shop robbery to look for fingerprints and evidence. Beach and Ray however spend the whole investigation gorging themselves on the sweets and chocolates talking about things like the colour of aniseed balls and the best type of chocolate bar. The investigation is ruined when it turns out that Beach is not wearing gloves and all the prints they have found are his. Plus the robber was wearing gloves anyway.

However they do find a blood and hair sample near a broken window. They decide to go to the hospital and nick anyone who has recently been admitted with a cut head. They end up bringing in some quite badly injured people for questioning, and Beach is soon convinced they have the man. Not only has he a cut head but he also has a quarter of a pound of cola cubes on him. The lady from the shop however says it's not the right man though Beach is convinced still and believes the forensics will prove it. However this proves a lame duck when they mix up the samples at the lab.

Beach decides the Good Guys need to sharpen up their minds so he takes them on a Sherlock Holmes weekend. Beach writes the script and plays Holmes with Ray naturally as Watson. However the weekend proves a disaster, as no one understands Beach's script and two hired actors refuse to come. Beach finishes as a gibbering wreck of tears whilst the others are still mystified by his script.