In Shakespeare's Romeo and Juliet, Romeo, believing Juliet is dead, visits an apothecary in Mantua to buy poison.
Through the unfortunate misadventures of these "star-crossed lovers," Romeo is unaware that Juliet has taken a sleeping potion provided by Friar Lawrence so she can avoid marrying Paris. (This all takes place after Romeo has been banished from Verona for killing Tybalt.)
"Apothecary" is another name for a druggist. It is important to note that it is illegal for an apothecary to sell poison in this city.
Such mortal drugs I have, but Mantua's law
Is death to any he that utters them. (66-67)
However, Romeo, upon entering the man's shop in Act Five, scene one, notices how poor business has been. In fact, the man is starving.
Art thou so bare and full of wretchedness,
and fear'st to die? Famine is in thy cheeks,
Need and oppression starveth in thy eyes,
Contempt and beggary hangs upon thy back. (68-71)
Romeo argues that the druggist will definitely die of starvation by not taking Romeo's money, or he can take a chance, not get caught, and live. The apothecary, on principle, dislikes taking Romeo's gold, but in light of his condition of near-starvation, he accepts, selling Romeo a potent potion that will quickly end one's life.
It is this poison, of course, that will end Romeo's life.