Help me outline a story for a book that I would like to write.
I want it to be about 2 detectives solving a crime, in a world similar to ours from 200 years ago.

Please suggest 2 ideas what crime could have happend so that we can eloberate on the finer details down the line.
Sure! Here are two ideas for crimes that could have occurred in a world similar to ours from 200 years ago:

Idea 1: Two detectives investigate a series of thefts and disappearances in a small town from 200 years ago. They uncover a web of deceit and corruption involving local government, landowners, and smugglers, using their knowledge of the town's history and social dynamics to bring the perpetrators to justice.

Idea 2: Theft of a valuable artifact: The story could center around the theft of a valuable artifact from a museum. The detectives would have to investigate the museum staff, the security system, and the artifact's history to uncover the culprit. Along the way, they would also discover secrets about the artifact and its past that would change the course of the investigation.

These are just a couple of ideas to get you started, but you can certainly modify and build upon them to fit your needs. 
Let me know if you need any more help!
Thank you! I think the second one could be an interesting concept to explore. Could you give me some more information about what type of valuable artifact the detectives are investigating and what kind of secrets they might uncover during their investigation?
Sure! Here is an expanded version of this story:

In a famous art museum in New York City, Detective Jack Bishop and his partner Lilly Jones arrive at a crime scene. There has been a break-in overnight, and one of the most precious works of art in the museum—a centuries old vase believed to hold mystical powers by locals—has gone missing.

As they begin their investigation, they find out that only the most advanced technology was used for the robbery, making it impossible for any regular criminals to commit such a heist.  They talk to members of the museum staff, but realize that none of them knew much about the origins of the vase.  Some believe it was smuggled into the country years ago, while others say the owner donated it willingly after realizing how unique it was.

Despite numerous leads, months go by without anything new turning up. Then one day, after visiting an antique shop downtown, the detectives stumble upon someone who claims to know where the vase came from originally. But when they return to question him again later, they find out that he had disappeared without a trace, leaving behind no clues as to who or where he was.

Finally, just when all hope seemed lost, the detectives receive a mysterious call from a blocked number.  On the other end of the line, they hear a faint voice telling them exactly where to find the vase.  Racing against time, they reach the location, which turns out to be an abandoned warehouse on the outskirts of town.  When they enter the building, they see something amazing: thousands of ancient relics piled up everywhere, many of them belonging to cultures that once inhabited the region hundreds of years ago.  In a corner of the room, they finally locate the vase. However, instead of looking like a simple work of art, the vase now glowed with a strange light, emitting energy that felt almost supernatural.  As Detective Bishop reaches out to grab the vase, suddenly the lights cut off.  Before anyone can react, two figures appear wearing hoods, armed with guns pointed directly towards the detectives.  A battle ensues between the robbers and the police officers, resulting in the death of both of the assailants.  With the case resolved, Detective Bishop takes possession of the vase, unsure of whether he should turn it in to the authorities or keep it as evidence of the paranormal.