This is an RPG module which I wrote and have run several times.
Here's the plot: a neighboring country has stolen an artifact from your country, and the adventurers have to cross the border and steal it back. On the way, they'll discover that the druids ruling the enemy town are turning people into werewolves and then enslaving them. Quick-witted groups can turn the werewolves, or the artifact itself, against the druids.
I often run this adventure in D&D 5e (with fourth-level characters), but it can work in any edition. Be careful not to allow characters that have access to flying, because those can skip over the bridge encounter.
If you need a teaser to send to your group, I recommend using this:
The Orb of Storms is an evil artifact, created hundreds of years ago by a very angry druid. The Orb loathes civilization, and it expresses its anger by controlling the weather. It calls downpours when it is mildly irritated, scaling up to hailstorms and tornadoes when truly enraged.
The Dragon Empress, owner of the Orb, keeps it in a state of mild irritation and uses it for agriculture.
The elves of Cedar Valley have suffered a bad drought this year, and the Empress has dispatched the Orb to bring much-needed rainfall. Everyone was very happy, yesterday evening, when we saw a storm cloud coming up over the mountains and entering the valley. But we woke up this morning and the storm cloud is in the wrong place: it's hovering over the Federation town of Freehaven, across the canyon.
It looks a great deal like the Federation has stolen the Orb of Storms. Your mission, this <insert day here>, is to cross the canyon into Federation territory, figure out what's happened to our artifact, and get it back before the Dragon Empress finds out it was stolen.
(The town you live in is mostly elven, and the Federation is mostly human, but feel free to play as any race.)
If you're new to being a DM, you might like my related site about How To Run A D&D Game.
Scene 2: Questions and Planning
In terms of structure, scenes 2-4 will happen for basically all groups, and scenes 5-7 are more sandboxy with branching paths.