The Calculus Affair (originally L'affaire Tournesol) is one of a series of classic comic-strip albums, written and illustrated by Belgian writer and illustrator Hergé, featuring young reporter Tintin as a hero.

The Calculus Affair is the eighteenth in the series.

The storyline

The story starts with Tintin and Haddock out for a quiet walk in the country, but the peace does not last long. By the second page of the book a metaphorical storm has broken over their heads, symbolized by the thunderstorm that spoils their walk. Mysterious events start happening at Marlinspike: mirrors smash for no reason, the windows shatter, and even Porcelain Ming vases are being destroyed by supposedly no force at all. The house is struck by lightening, and the ghastly Jolyon Wagg turns up uninvited. As he is leaving shots are heard in the park. The only person unconcerned at all these events is Cuthbert Calculus; a couple of days later Calculus leaves for a conference in Geneva.

When he is gone, things are calmer. Tintin suspects that the strange events may have been connected with Calculus, and suggests to Haddock that they have a look inside his laboratory. They find a strange sonic device and are surprised by an eastern European in a rain coat and a mask. The intruder escapes after punching Haddock. Concerned that Calculus is in danger, Tintin and Haddock decide to follow him to Geneva.

In Geneva their fears are realised and Calculus is abducted before they can reach him. Tintin and Haddock learn that the sonic device that they found in the laboratory was responsible for the breakages at Marlinspike, and that rival teams of agents from both Syldavia and Borduria are trying to steal the device for it's military potential and to get Calculus to give them his secret plans. After a long and complicated chase Tintin and Haddock rescue Calculus from prison and drive to safety in a tank.

Memorable scenes

• The arrival of Jolyon Wagg.

• The day trippers camped outside the gates of Marlinspike (Hergé himself can be spotted in the crowd).

• The painstakingly accurate drawings of Geneva, the Hotel Cornavin, the railway station and Cointrin aeroport.

• A famous sight gag from this album is the one where Captain Haddock tries to get rid of a piece of band-aid, but it keeps returning to him.

• The car chase with the mad Italian driver. When a gendarme eventually stops them and asks for his name, he recites it in full: Arturo Benedetto Giovanni Giuseppe Pietro Archangelo Alfredo Cartoffoli da Milano. The gendarme weakly tells him not to do it again.

• The tank chase and the escape through the "weakest spot" at the customs post.