Dirgelwch y Llythyr Coll (Llan-ar-goll-en)

Dirgelwch y Llythyr Coll (English: The Mystery of the Lost Letter) is the 20th episode from the first season of Llan-ar-goll-en.

Plot
Ceri the Dog-tective has a heavy cold and doesn't feel well enough to help Prys with his detective work. Can Prys ar Frys solve today's mystery without her help?

Why It Rocks

 * 1) The plot of the episode is very similar to Blue's Big Musical Movie, where the idea of the live-action men of both shows not being able to solve the mysteries on their own comes up, and is eventually resolved.
 * 2) Some funny moments, as usual. Like the reaction Tara and Mrs. Tomos have to Ceri being the one to have stolen the mystery of the day.
 * 3) A sad but very important scene where Prys worries about not being able to solve the mystery of the day without Ceri by his side. This shows that he is very dependent on her, which makes you feel satisfied when he actually ends up solving the mystery.
 * 4) For once, Prys FINALLY solves the mystery of the day without anyone else's help (technically). Mrs. Tomos and Tara are rightfully proud of him.
 * 5) *He also gets to say Ceri's usual catchphrases once he figures out the mystery.
 * 6) Beautiful ending where Ceri reveals to have been faking sickness the whole time, only in order to gift Prys a letter, thanking him for being the best detective in Llan-ar-goll-en. Prys is almost in tears.

Bad Qualities

 * 1) It uses the "forgotten birthday" cliché.
 * 2) Plothole: If Ceri was pretending to be sick, why does she look and sound fine in the scene used once every episode where Prys and Ceri leave their lighthouse and get ready to solve the mystery of the day?