There are some episodes that imply that the library is behind the curious door by the balcony. In episode #84, The Case of the Gallant Grafter, Della says to Perry, "Gertie put him in the Law Library." She then opens the door by the balcony and Perry's client, Edward Nelson, walks out. In episode #104, The Case of the Nine Dolls, Perry says to Della, "Take Peggy to the Law Library!" The three then head for the door by the balcony. In episode #129, The Case of the Meddling Medium, David enters from the door by the balcony. Della comments at Perry's surprise: "You said he could use the Law Library!" In episode #134, The Case of the Left-handed Liar, David and Casey enter from the door by the balcony. The dialog implies that they had been waiting in the Law Library.

From Charles Richmond, 4/4/07: "In TCOT Negligent Nymph (#12), Perry tells Della to put Sally Fenner in the Law Library. When Lt. Tragg leaves, Sally comes from the "curious door" next to the balcony. That implies that the Law Library is next to the balcony."

Episode #14 The Case of the Baited Hook
First season, 12/21/57.

Picture 1 The entrance to the law library is to the right of the bust of Voltaire in Perry's private office. As Perry walks towards the door, the wall can be seen to be flat although there is a rather strange change in color and texture.

Picture 2 At the door, it can be seen that the walls appear to join at an angle greater than 90 degrees. The door opens outwards.

Picture 3 Inside, the walls on either side of the door can be seen. At the right is a raised bookcase set back on an angled wall. Further right, another door.

Picture 4 Later in the scene, Perry leaves the library to talk with Tragg. As he leaves, the wall to the right of the door has changed.

Picture 5 The wall outside has changed as well. Very curious.

Picture 6 On the wall to the right of the door in picture 3, there are two raised bookcases with a door to Della's office in between.

Picture 7 As Tragg opens the "wrong" door, more of the library is seen. On the rear wall, to the left, a glimpse of the door into Gertie's office.

Episode #87 The Case of the Singing Skirt
Third season, 3/12/60.

Picture 8 With the viewpoint near the right side of the door, the concept of an angled entry wall is confirmed. Through the door, the left side of the wall behind Perry's desk can be seen. The door however now opens inwards! The entry wall style is similar to picture 4.

Picture 9 As the scene progresses, tall, floor-mounted bookcases are revealed. The bookcases are different and set back further than in picture 4.

Picture 10 Della's door is missing. Further on, there is a safe, the apparent point of this excursion into the law library.

Episode #136: The Case of the Renegade Refugee
Fifth season, 12/9/61.

Picture 11 With the viewpoint to the left of the door, the balcony window can be seen behind David Gideon as expected. The door opens inwards again. The angle of the entry wall is not as acute that seen in picture 8. It is similar to that seen in picture 14. The interior around the doorway is has changed yet again.

Picture 12 With the viewpoint further to the left, the wall between the door to Della's office and the balcony is now partially visible. Della's door is closer to the Law Library. There is now quite a bit of space between the end table and Della's door. The bust of Voltaire has curiously moved into this void.

Episode #162: The Case of the Weary Watchdog
Sixth season, 11/29/62.

Picture 13 The entry is again different, but the door still opens inwards, and the bookcase on the right is similar to that seen in picture 3. Perhaps that is Della's door further to the right?

Picture 14 The viewpoint here is to the left of the entry door. As expected, the balcony wall can be seen through the door behind Sgt. Brice. The front edge of Perry's desk is presumably hidden behind Lt. Andy and Sgt. Brice.

[The Office][Perry Mason TV Series]