Sorry if this is kinda bad but it's for two reasons:

a) Cause I've never done a Carmen one before

b) Because a Scottish water van is driving up and down outside announcing our water is getting cut off because of a burst water main

I own nothing Carmen Sandiego related except for Treasures of Knowledge and Secret of the Stolen Drums. I'm not making any money from this.

Spoilerish for Treasures of Knowledge.

Puzzle

The Chief watched Jules Argent leave her office, having been assigned her new partner. Shadow Hawkins, a keen rookie, with a fondness for gadgets, and a tendency to charge right into a situation, without thinking.

"Hopefully you could knock some sense into him," she had said to Jules, who had accepted reluctantly. Everyone knew why that was. She didn't want to work with Shadow. She wanted to be back working in her old partnership.

Half Brazilian Carmen Isabela Sandiego had been not only Jules' partner, but also ACME's golden girl. She and Jules had partnered each other for three years. They had been the best partnership ACME had ever seen, and solved cases that would have perplexed even the best agents. And the best of friends as well, although Carmen was the only person that had called Jules by her full name, Julia.

And then one day, not long after they got back from Romania, about four months ago, Carmen disappeared. They later heard that same day that she had turned on ACME and joined the organisation which she had displayed so much interest in investigating: VILE. Every person under ACME's roof was in shock, and many people blamed Jules for her leaving. She had been upset but what could she do? Nobody knew how or when or why Carmen had gone, but she had. A twenty-man (and woman) team had searched for her, with their scouts across the globe keeping an eye out for her. All proved negative.

Until one day, a call came in from Ana, who was the last agent to see Carmen and Jules before they returned to New York. Carmen was spotted in Timiosara. Similar calls came in from all across the world. Hannah in Melbourne. David in Rabat. Charlotte and Nicola in Glasgow. Paul in Tokyo. Patrick and Lucas in Rio de Janeiro.

The Brazilian call also mentioned that a very rare book, The Travels of Marco Polo had also been stolen. Carmen had always been interested in it and it didn't take anyone long to put two and two together.

It when the last alert came in that the Chief had had enough. She assigned Jules to a new partner on a new case. Shadow had completed his training and was eager to set off; Jules slightly less happy about having to chase her old partner, and her best friend.
Maybe, when Jules found Carmen, she might be able to get to the bottom of this. Why she had done her disappearing act. Until then it would remain a mystery.
Carmen had always loved puzzles. Now she had created a life size one, and it would take all of Jules' wit, intelligence, and strength to solve it.