Very little is known about Herr Thiessen prior to his involvement with the circus, apart from his date of birth (September 9th, 1846), and the fact that he is an accomplished clockmaker.
In 1885, Thiessen meets Ethan Barris, who commissions a clock for the circus (although Herr Thiessen is not told what will happen to the clock or where it will be used). Thiessen proceeds to create a remarkable "dreamlike" black-and-white clock which, amongst other things, has the ability to change colour (this clock turns out to be the clock in the circus' courtyard). Thiessen never hears from Ethan again, but he sometimes wonders what happened to the clock.
Four years later, during a holiday in France, Thiessen hears of the Night Circus from a winemaker, who mentions that the clock in the courtyard is reminiscent of Thiessen's own work. Curious, Thiessen decides to visit the circus that evening andmakes the discovery that it is indeed his clock within the courtyard. Thiessen become enchanted by the circus by the end of the evening, and over time his other commissons become influenced by the circus.
Thiessen is also recognised as being the unofficial leader of the 'reveurs' - the title for anybody who is a devoted fan of the Night Circus. From 1891, Thiessen begins to note down his observations about the circus, and after conversing with a newspaper editor, he is convinced to allow some of his journal experts to be published by the paper. Thiessen continues to write for the paper, and the articles are translated and published in papers across Europe - these articles play a significant part in making Thiessen so important in the eyes of the reveurs. Thiessen begins to make clocks for reveurs that are based around the circus, and he unintentionally creates a type of uniform for reveurs - black or white clothing with a hint of red. Thiessen's position as leader of the reveurs gives him some exclusive benefits, such as an invite to the circus' 13th anniversary celebration in 1899.
Thiessen begins a friendship with Celia Bowen after she writes to Thiessen, who notices the keen detail that she has when writing about the circus. In 1895 Thiessen and Celia finally meet after she requests a tour of his workshop, and the two remain close friends across the years.
Herr Thiessen dies on the evening of October 31st, 1901 in London after being hit by a knife thrown by Chandresh Lefevre (The knife was originally intended for the man in the grey suit, who dodges the knife whilst talking to Thiessen). Thiessen dies despite Celia's attempts to heal him, leaving her with a deep feeling of guilt over his death.
After his death, Herr Thiessen is kept in memory by the circus - beneath his clock, there is a silver plaque that reads:
Friedrick Stefan Thiessen
September 9, 1846 - November 1, 1901