A Wonderful Journey

A Wonderful Journey is the slated title for the season 1 finale, which is booked as being an hour-long special.

Number
It is listed as "EPISODE 138 - 140" indicating it is 3x the length of a usual episode. Normally that's about 22 minutes filling a 30 minute block, but that can be cut down to about 20 minutes each by not duplicating the opening/ending songs, which is how it could fit into 60 minutes.

This is revealed through a PDF of all the episodes revealed on PBS Pressroom's website under "ELINOR WONDERS WHY Episode Descriptions" from http://pressroom.pbs.org/PBS-Kids/ELINOR-WONDERS-WHY which can be viewed at https://pressroom.pbs.org/-/media/Images/01-KIDS/ELINOR-WONDERS-WHY/Elinor-Wonders-Why_Episode-Descriptions-101-140_V6_June_26_-2020_FINAL.ashx or the copy of it on the wiki here:
 * File:Elinor Wonders Why Episode Descriptions 101-140 V6 June 26 2020 FINAL.pdf

Plot
Elinor and her friends have a curious and fun adventure when they go camping with Ranger Rabbit to Hidden Lake, a place in the forest that they've never been to before. On their wonderful journey, they bump into Bianca, an inventor and good friend of Ranger Rabbit's who studies frogs. But, on a hike to help Bianca observe them, the kids discover that the frogs seem to be missing from the lake. Why? It's up to Elinor, Bianca and her friends to solve the mystery of the missing frogs. Together, they discover the source of the problem: the lake is being dammed by sticks from a nearby road clearing project, causing the frogs to leave. By asking questions and getting inspiration from nature, the team invents a new tool that looks like a frog’s tongue to break loose the dam and save the frogs!

Songs

 * Elinor Wonders Why Theme Song
 * 'Cause It's Make Believe
 * $7.50 Once a Week
 * Dance The Gloomies Away
 * It's the Pop
 * 'Cause It's Make Believe (reprise)