Phaedo.

Phædo or Phaedo, also known to ancient readers as On The Soul, is one of the best-known dialogues of Plato's middle period, along with the Republic and the Symposium. The Phaedo, which depicts the death of Socrates, is also Plato's fourth and last dialogue to detail the philosopher's final days, following Euthyphro, Apology, and Crito. In the dialogue, Socrates discusses the nature of the afterlife on his last day before being executed by drinking hemlock.