Frank, a friend of Walter

Walter decided to introduce his new invention to his friend Frank. So he called him.

In the late afternoon Frank arrived in front of Walter's house. Quickly he turned off the engine of his car and rang the doorbell.

Seconds later, this opened.

"Walter?" cried Frank. Then he saw that light came from the basement, where Walter also had his experimental laboratory.

He quickly went down the stairs and opened the door ...