In Biggles – Secret Agent, the Kleishausen was the one and only hotel in the Lucranian village of Unterhamstadt. It was, according to Biggles, a good hotel, built on the pattern of the old coaching stations common in France and Germany. Johns described the hotel in great detail, probably to add some "atmosphere". It was alarge, rambling building, rather impressive and obviously medieval in inspiration. It had a tower and gables on its roofs, each with diamond paned windows. The whole building was decorated with ornate timbering in a style which, according to Johns, was known in England as "balck and white". The entrance to the hotel had an imposing porch with the insignia of several international touring associations.
The hotel had two floors. A secret underground tunnel led from Room 17 on the upper floor to Unterhamstadt Castle.
After being kidnapped by Erich von Stalhein, Professor Max Beklinder was taken to Room 17 of the hotel. There his death was faked for the benefit of the undertaker and he was then conveyed via the tunnel to the castle.
Biggles and Ginger stayed at the hotel when they arrived to ascertain the fate of the Professor. The Professor's son, Gustav Beklinder, also stayed at the hotel when he came to Unterhamstadt to look for his father.