Flick
The song that Luke heard just before he felt his consciousness fade was graceful and, at the same time, sad. The imperturbable tone of the woman who sang this tune was quite familiar to Luke, somehow.
The half-wolf was warned by Alexis that seals could be confusing, and that literally anything could happen inside a white cube, and he thought he was prepared for anything. However, there was no way for Luke to know whether he was ready to face his past or not.
Would Luke and Masink regret the most important decisions of their lives? That was what the white cube would test.
If they both regretted it, they would both be imprisoned until someone was willing to set them free, and if one of the two didn't regret it, that one could free himself.
In this spiritual and mental prison, there were no ways for Luke to lie to the cube, nor to himself.