Their first case takes Mike and John to Snowdonia National Park as farmer Pam believes a wild Puma has been attacking her sheep. As she leads them through the woods to the location of a 'big cat' sighting, John is keen to investigate further, whereas Mike seems sceptical. John plans to capture the cat, but will he succeed?
The duo then travel to Bala to investigate the mysterious monster of Llyn Tegid - 'Teggie'. A sailing trip fails to uncover new evidence of the beast, so John and Mike chat to some of the local fisherman to hear their tales of previous sightings.