The group arrives at the bridge crossing. The guards on this side of the bridge are missing: the doors are broken into and there are signs that the guards were dragged to the canyon. If the group searches the guard huts, they find a few healing potions the guards were saving for emergencies.
On the other side of the bridge are five humans. This includes four guards: Roger, Aaron, Fred, and Susan. They all have chain shirts, crossbows, and swords. The fifth human, Lord Bruce, is unarmored; he's wearing a cloth tunic with some holes in it which look like they might have been made by weapons. He's got a big axe strapped to his back. He has a long scraggly beard; he's wearing shorts but no shoes. Bruce shouts: "No crossing! The bridge is closed!"
(Bruce wears a silver necklace which is mostly hidden under the beard. This is a silver necklace of Malanel, which allows the druids of Freehaven to give him unbreakable orders. Bruce is mostly a willing servant of the druids, though -- they pay him well. Bruce can't remove the necklace, and it gives him a rash, but taking it off him (and removing the mind control) has no immediate effect.)
The four human guards are unhappy about Lord Bruce's presence, but Lord Bruce has a document giving him command over this outpost. The document is signed by the druid Erik the Bear and is clearly legitimate. If presented with clear evidence that Lord Bruce is a werewolf, the guards would stop obeying him and either surrender or flee. In the meantime, they'll obey orders to shoot at anyone crossing the bridge.
Telling the human guards that Lord Bruce murdered the elven guards will make them unhappy -- the human and elven guards were friends, and in at least one case were romantically involved -- and it might make them stop shooting for a few rounds, but ultimately it would take a difficult skill check to persuade the human guards to turn on Lord Bruce in this way.
Bruce's title of "Lord" is mostly fiction; he doesn't have any land, any money, or any manners. Bruce is, in fact, a werewolf, and he obeys Erik the Bear so long as Erik pays him. Yesterday, Bruce came to this outpost, showed the guards his papers, and then left at nightfall to cross the bridge. He killed the elven bridge guards, attacked the couriers carrying the Orb of Storms, and returned to Freehaven with the Orb. Now he's standing here with orders to prevent any adventurers from crossing the bridge.
Bruce is both stupid and gullible. Any of a number of ploys might be sufficient to get him to let someone cross the bridge, including but not limited to:
I'm a baker and I have fresh bread, would you like some? The guards will vouch that I cross every day.
I'm a hunter and I just killed a deer, would you like half?
I challenge you to a duel on your side of the bridge!
I will pay you money to let me cross.
Hey, sexy, let me across the bridge so we can make out!
Your master Erik gave me a letter for you, let me cross the bridge so I can deliver it!
Most of these should require a skill check. Most of these will only allow one person to cross, so this might lead to a situation where one person crosses and then stops Bruce from chopping the bridge down while the rest of them cross.
If anyone tries to cross the bridge without Bruce's permission, the guards will fire crossbows and Bruce will move to cut the ropes holding the bridge up. Characters might need skill checks to stay on the bridge as Bruce cuts the rope, and they might need skill checks to cross the bridge quickly without tripping on the planks. It should take a fairly difficult skill check to cross the bridge in one turn.
If Bruce cuts a rope and someone fails a skill check to stay on the bridge, it's best to tell them that they're "hanging by their hands" from the bridge, rather than narrate them falling fifty feet to their death. If Bruce cuts the second rope, the bridge falls into the water, which leads to a failure for the scenario. But Bruce only goes to cut ropes if nobody is distracting him, so hopefully the group will avoid this.
As a werewolf, Bruce is immune to weapons unless they're magic or silver. The group should not have any magic or silver weapons at this stage, unless they went back to town to get some silver weapons at the first sign of werewolves. The group might have some silver coinage, but it's difficult to seriously injure Bruce using coins. Bruce is vulnerable to magical attacks, to alchemist's fire, or (most easily) to being thrown into the canyon, with a 50 foot drop into the river. If this happens, Bruce survives the fall but he gets washed away by the river and eventually drowns.
In combat, Bruce fights using his greataxe; he doesn't bother to defend himself from weapons because he's immune to them. If the group manages to hurt him somehow, he drops his greataxe and switches to a hybrid wolfman form, which causes the guards to stop helping him.
(If someone is bitten by a werewolf, they have a chance to become a werewolf themselves. The character notices no ill effects unless the group tries to take a long rest, in which case the character is likely to attack the rest of the group in their sleep. Note that werewolves cannot remove the silver necklaces of Malanel, and being in contact with a necklace (even just touching it) allows the druids to command them. A temple in Cedar Valley could perform an hour-long ritual to remove the lycanthropy.)
If Bruce is revealed as a werewolf and then defeated, the guards surrender and apologize. They didn't believe werewolves were even real, and they certainly never meant for one to kill their friends on the elven side of the bridge. The guards are willing to answer questions about Freehaven or about Lord Bruce. If asked directly, they have a few healing potions they can give the party. The guards might give the group directions to Crazy Ivan, in town, who has an interest in monsters, including werewolves.
Interrogating the guards might reveal in passing that the town of Freehaven has a ban on all silver, including silver money. Freehaven uses gold pieces, steel pieces, and copper pieces. This ban has been in place for three years.
If the players wanted, at this point they might try heading back to town and getting silver weapons for everyone. Nobody has ever thought to try this. (And I don't volunteer the suggestion, since it would let them skip half of Scene 5.)
Sidebar: Lycanthropy and You
Bruce is a "full" werewolf, one who has embraced lycanthropy. He's immune to non-silver weapons even in his human form, and he can change form at will as a bonus action.
Most of the werewolves we'll encounter are "afflicted" werewolves -- people who were bitten, but who haven't had the time or the inclination to fully embrace their werewolf-ness. These characters change form involuntarily, and they don't have special immunity to non-silver weapons when not a werewolf.
Lycanthropy is inherently evil, and all "full" werewolves are inherently evil. If a player character reaches this status somehow, they become an NPC.