Jack Frost is the sixteenth episode ever made in Season 6.
Percy and James have to collect coal for the stations to last during an upcoming snowstorm, and Thomas warns them about Jack Frost. James is dismissive, but Percy is uncertain if Thomas is telling the truth. Percy eventually finishes his deliveries, but his last stop needs more coal and so Percy gives them the coal from his bunker and stays on a siding, where he is soon covered in snow and icicles. James later passes by and, upon seeing a snowbound Percy, mistakes him for Jack Frost and runs off, terrified. When Percy returns, James is bragging to the others that he saw Jack Frost. Percy adds that James was scared of him too, but the red engine is still able to make good humour of the situation.
- The amount of snow on Percy's face decreases at one point.