The chapter presents a 2-year-long process of creating a combined learning environment in a high-school class. The environment consisted of teaching mathematics in a classroom and collaborative problem solving in an asynchronous online forum. The process is described and analyzed according to the principles of one of the methods of narrative research, known as virtual duoethnography. That is, the exposition is shaped as a conversation between imaginary characters representing the teacher, the students, and the researchers, who bring their unique perspectives on the process in question. The conversation, though imaginary, is grounded in the real data collected for 2 years from classroom observations, student interviews and content of the online problem-solving forums. Finally, two conclusions are substantiated. First, the process of incorporating on-line collaborative problem solving in mathematics teaching can be decoded as a process of diffusion of an innovation, in the following meaning: the stages of the process, from the initial antagonism requiring persuasion to the final confirmation signaling acceptance of new problem-solving practices by students, matched the stages described in the Everett Rodgers’ theory of diffusion of innovation. Second, there existed a bilateral effect between the online environment and the classroom environment, which eventually led to the integration of the two environments into a new, unique, and effective learning space.