A young man, in the full flower of his youth, comes across very lengthy, complicated and intricate instructions on how to construct an apparatus of some kind. He becomes intrigued and then obsessed by these instructions and devotes all of his hours to the building of this machine, of whose function and purpose he is completely ignorant and wants desperately to find out.
Years go by, as he painstakingly follows each step of the seemingly endless instructions, but he is not concerned at all by the passing of time, so dedicated is he to his task. And in any case, he is convinced that once the machine is completed, all of the work and the time he had spent on it will be retrospectively justified and his actions will gain the meaning that they presently lack.
And so, decades after beginning the construction, the last component is ready to be put into its place. All that is needed to do is to fasten it with the last bolt and the apparatus will be complete. As he is doing so, he realises he has become an old man and that he is now living out the final moments of his life. As his vision grows dim, he sees for the very first time that the apparatus he has spent all of his life building is a coffin and that nothing remains for him to do but to place himself in it for all eternity.