The Devil's Due

The Devil's Due is a side quest in Fallout 4.

Quick walkthrough

 * 1) Investigate the Salem Museum of Witchcraft.
 * 2) Listen to Private Hart's holotape.
 * 3) Explore the museum.
 * 4) Listen to Sergeant Lee's holotape.
 * 5) Complete delivery of the egg OR
 * 6) Return the egg to its nest.

Detailed walkthrough
On the exterior west side of the witch museum is a body; on it is Private Hart's holotape. When you listen to the holotape it will be clear that they were running from something and ran into the museum. Enter the museum via the cellar ground door a few feet away from the body. While in the museum there is growling and some body parts dropping from holes in the ceiling periodically as you make your way through. Make your way to the second level. In the room behind the closed door there is a wandering deathclaw (type depends on your level). Upon killing it, you can loot the body or look around the floor near it in the bathroom to find Sergeant Lee's holotape, and around the body a few broken deathclaw eggs and one pristine deathclaw egg.

You have the option to either continue the delivery of the egg in Diamond City, where you will awarded 200 caps (plus an additional 100 with every persuade approval) and the recipes to craft tasty deathclaw omelette and Deathclaw Wellington; or you can return the egg to the nest west of Parsons Creamery where a friendly deathclaw will appear and you can find a deathclaw gauntlet next to the nest. Finally, it is possible to take the gauntlet without returning the egg, allowing you to sell the egg to Wellingham normally. Please note that the friendly deathclaw will turn hostile if you try to leave the area without returning the egg. You can still fast travel while the deathclaw is still friendly. Simply grab the gauntlet and fast travel to Diamond City without leaving the immediate area which would make the deathclaw hostile and prevent fast traveling.

Companion reactions
Companions will react based on the decision in the quest. If one returns the egg to the nest:
 * Piper, Nick Valentine, and Codsworth like this act.
 * Curie, Cait, Preston Garvey, Deacon, and Strong dislike this act.
 * Danse hates this act.

Companions will react based on the decision to steal the egg after returning:
 * Hancock, Curie, Deacon, Cait, Preston Garvey, and MacCready like this act.
 * Piper, and Nick Valentine dislike this act.
 * Danse hates this act.

Bugs

 * The friendly deathclaw protecting the nest will be hostile if you are wearing a targeting power armor helmet. Putting the helmet on after completing the quest by returning the egg will immediately turn the deathclaw hostile.
 * Berry mentats will also trigger a hostile status.