Riddles in the Classroom

We started off the year by doing a Nature of Science (NOS) lesson with three 10th grade sections of Bio 1.  The NOS lesson was based around the historical case of Beriberi; but presented to the students in the form of a riddle.
The idea of using riddles in the classroom came about over the summer while working at a science camp.  During down time, a co-mentor of mine, gave her students riddles to figure out.  The students loved it, especially when we wouldn't give them the answer.  :)
There is a connection between solving a riddle and problem solving in science: you're faced with a problem;  you develop a hypothesis; you ask a question; you get an answer; you redirect your questioning based on the gathered evidence and hopefully end up at a solution.  Some of the riddles were easier than others, as the students quickly found out.  For the harder riddles, the students worked in groups, each group asking questions as we circulated through the class.  When the students reached a point when they felt as though they were stuck, they were allowed to collaborate with other groups and compare information.  Without realizing it, the students were actively engaging in a modified version of the "scientific method."  Shhhh!
So back to Beriberi...
The students moved through the investigation just as Eijkman had.  At various points along the way, the students were prompted to reflect on the information that Eijkman had gathered thus far; speculating as to what they thought was occurring.  I even overheard some students stating that the Beriberi lesson was "like a riddle."  Roughly midway through the lesson, the students were given the task of developing an experiment that they thought may lead to solving the mystery of Beriberi.  They were to take on the role of an assistant researcher to Eijkman; placing themselves within the context of the historical research.  The only contraints placed on the students was that they were only allowed to use the tools and information available to Eijkman at the time of his initial research.
The ideas and experiments the students came up with blew us all away.  Some of the groups had elaborate experiments that included controls, independent & dependent variables, etc.  At this point they had not been formally introduced to the scientific method, but they were doing it!
At the end of the unit, the students were told the conclusion of the Beriberi mystery.  They then compared their ideas and experiments to those of Eijkman and his scientists.  After the unit, the students went through a more guided lab that reinforced experimental design.
By designing the first lesson of the year similar to a riddle, the students were immediately engaged in this activity.  They had fun and opened up to us, as well as to one another.
As subsequent lessons are designed, they are referring back to the principles of NOS as well as linking common themes throughout the year.  Will students be able to build upon the knowledge that they are actively a part of constructing?  We shall see...