Act 1 - the perplexing video or picture. Ask students what questions they have about what they've seen. Have them make estimates about what they think the answer is. Have them brainstorm a list of necessary additional information they think they will need to get to the bottom of things.
Act 2 - provide more information. This could be a collection of data, additional pictures showing measurements that were taken, another video where students see that data collection and make their own notes, or a short lesson that provides the mathematics that are needed to solve the problem. During Act 2, students work together to process the information they have collected to try to answer the question.
Act 3 - provide the answer. This isn't the teacher saying "The correct answer is...." Rather, you show them the answer. The complete video that captures the end result. A picture showing the final sum. A link to a website that contains the answer. Act 3 can be used to reflect on the process. How close were our guesses, how accurate was our method of solving the problem, what follow up questions can now be answered or explored?
I recently went on a family trip to Wisconsin and we went canoeing/kayaking up a small river. A few minutes into our paddling, we came across this lock and dam:
What questions do you have?