I ended up with the daydream idea, or, the introduction to the daydream scene.
Here Mary is sitting writing in her diary about her day and reflects over the conversation they had that evening. She falls asleep while writing and we can see lightning flashing through the windows. Some greenish cloudy/smoke appears from her diary coming from her writing. In the cloud, a face appears in the flashing of the thunderstorm, the face of professor Frankenstein.
