Das Rätsel der 43

The boys are sitting in the cafeteria. Sheldon is making recordings on the side, about a containment field for a wormhole. This should be a portal to a parallel world. Howard asks if he intends to build this, but Sheldon brushes him off.. Howard makes the others aware that Sheldon disappears at the same time every day. Even in his calendar, there are no entries for a period of twenty minutes.

Leonard is visiting with Penny. When she receives a text message, Leonard becomes curious. The message is from a classmate with whom Penny wants to study for the test. Leonard asks her to write to her friend that he should not disturb her. But he immediately realizes that Leonard has asked Penny to do this. Leonard becomes even more jealous and would rather accept that Penny fails.

Howard and Raj try to figure out what Sheldon's twenty minute break is for. He has no time and waves the two off. They meet Alex, but he also doesn't know where Sheldon goes.

They follow Sheldon to the basement, where he disappears into a lumber room. They listen, but the noise does not make it outside. The group puts their heads together, but they cannot come up with an explanation for what Sheldon is doing there.

Leonard is standing in the apartment looking through the peephole. He wants to see Penny's classmate when he comes over to study. Sheldon clarifies to him that Leonard has grounds to be jealous, because after all there is plenty of competition for Penny. Leonard trusts Penny and convinces himself that he has no reason to be jealous.

At night, Raj and Howard sneak into the basement of the University. They want to investigate the storeroom. Once Howard has managed to procure entry, the two search the room. But no clues are available except for the number "43" on a blackboard. They see that they are faced with a new mystery.

As Penny says goodbye to her visitor, Leonard catches them in the stairwell. He wants to convince Penny's classmate that she has a scary boyfriend, without outing himself. But Penny has overheard him and waits in the stairs for him.

In the cafeteria Alex meets Leonard. They talk to each other and Leonard tells her about his problems with Penny's classmate. Alex tries to calm him down and makes it clear that even he is definitely getting flirted with. But Leonard laughs about that and leaves.

Penny meets Leonard in the hallway. Leonard wants to apologize, and Penny opens up to him that due to a photo left in her apartment, her classmate knew a long time ago who Leonard is. She makes him a declaration of love. But then Penny is afraid to cry and quickly runs away. In the apartment, Leonard finally receives news from Alex that they are obviously flirting, but Leonard doesn't believe this and maintains they are just friends.

Howard and Raj, in their investigation of the number "43" in the store room, have installed a security camera. Now they want to see the material. They can see how Sheldon is performing a wormhole generator test. The number "43" is intended here to represent the universes already tested. They see how Sheldon sticks his head into the wormhole. However, an alien attacks him there, which apparently eats his face. They both begin to scream. Then Sheldon comes in and startles them with an alien mask. He explains that he found the camera and video-taped a prank to fool them. In addition he holds that his twenty minutes is used to relax, refuel, and turn off his mind.

In the final scene, we see Sheldon go into the room. He brings a hacky sack out of his pocket and begins to play. But as the Hacky Sack falls to the ground, he becomes certain that he will never again be able to get to 43.