Tras el cristal
Original poster
Directed by	Agustí Villaronga
Written by	Agustí Villaronga
Produced by	Teresa Enrich
Starring	Günter Meisner Marisa Paredes David Sust
Cinematography	Jaume Peracaula
Edited by	Raúl Román
Music by	Javier Navarrete
Production company	T.E.M. Productores S.A.
Distributed by	Cinevista Video
Release date	3 March 1987 (Spain)
Running time	110 minutes
Country	Spain
Language	Spanish
Box office	31.624.135 Pesetas[1]

Tras el cristal (English: In a Glass Cage) is a 1985 Spanish art house horror film written and directed by Agustí Villaronga and starring Günter Meisner, Marisa Paredes and David Sust. ^[2] The plot follows an ex-Nazi sadomasochist child abuser who is now immobile and depending on an iron lung to live. A young man who comes to nurse him was one his former victims years before.

Klaus, a former Nazi German doctor who practiced horrific experiments with children during World War II, has continued with his sick attraction for torturing and killing young boys during his exile in Catalonia. His latest victim is a child he has tortured and dangling from the ceiling he kills him with a blow to the head, taking photographs of the crime. This sadistic act has been witnessed by Angelo, another of Klaus victims, who has spied him from a window,later stealing the tortured incriminating writings and photographs of the doctor's crimes. Klaus tries to commit suicide jumping from a tower, but he survives. As a result of his failed attempt he is now unable to breath on his own; confined to a glass cage; immobile and depending on an iron lung to live.

Some years years later, Klaus is taking care of by his wife Griselda and their daughter Rena in a lugubrious large house in the county. Griselda is unhappy in Spain and, overwhelmed by the task of looking after her husband, she secretly wish he would just die. Then a young man appears offering his services as a nurse to help taking care of Klaus. Griselda takes an instant dislike towards, Angelo, the young man, and does not want to hire him, but Klaus insists that he should stay. Angelo actually has not nursing skills, which Griselda soon discovers, but even then Klaus refuses to get rid of him. The striking looking young man with big scars on his face, was one of Klaus victims and they had a sickening sadomasochism relationship. His instinct are, like Klaus's, disturbed. Angelo's aim is to take revenge from Klaus, but also ultimately to take his place. The two men bond quickly forming a perverse disturbing relationship. Angelo reads Klaus passages from the diaries he stole in which the doctor described in detail how he tortured his young victims. Recreating what Klaus did to him, Angelo strips and masturbates in front of Klaus glass cage. He then calls Griselda. She tries to runaway from him after seeing what he has done, but he kills her hanging her from the rails of the second floor.

The next day Angelo fires the housekeeper taking over the house with Rena's help. Rena is not disturbed by her mother's absence, she was harsh on her and Rena feels much more comfortable under Angelo's care. Angelo proceeds to continue with the doctor's experiments delivering young boys next to Klaus's glass cage. Angelo lures a child to the house with the excuse of needing help with carrying the groceries. He ties the boy to a chair and in front of Klaus kills the boy injecting him through the heart with a needle filled with gasoline. A second boy is brought in and Angelo kills him cutting his throat. Fearing that Angelo is out of control and that his life and Rena's are in danger, Klaus tells his daughter to runaway to the near village with a message asking for help.

Angelo discovers Rena when she was trying to escape and brings her back to the house. He dominates her, sometimes assuming a parental protective role and some other through terror and violence. Finally Angelo removes Klaus from his iron lung to die asphyxiated while emulating the scene of his own abuse, in Rena's presence. Once Klaus is dead, Angelo takes his identity totally getting into the artificial lung and makes Rena take his.

• Günter Meisner as Klaus
• David Sust as Angelo
• Marisa Paredes as Griselda
• Gisèle Echevarría as Rena
• Imma Colomer as Jornalera
• Josue Guasch as Niño Cantior
• David Cuspinera as Niño barracon
• Ricardo Carcelero as Angelo Niño
• Alberto Manzano as Niño gitano

It was the directorial debut of the Spanish filmmaker Agustí Villaronga.^{[3][unreliable source?]}

• In a Glass Cage at IMDb
• In a Glass Cage at AllMovie