A lot of younger people do not seem to understand why the story is called "The Chaser." The meaning of the title "The Chaser" is very simple, although the term "chaser" may not be as commonly used as it was when John Collier wrote his story. A chaser is a drink that is taken to follow the first alcoholic drink. The chaser may be alcoholic or non-alcoholic. For example, a person might drink a straight shot of whiskey and follow it immediately with a small glass of water to dilute the whiskey already in his stomach. One common combination at bars is a shot of straight whiskey followed by a small glass of beer.
The chaser in Collier's story is a poisoned drink intended to kill the woman who is suffocating the hero with too much love and possessiveness. The original drink was the love potion he bought to make her fall in love with him. The word "chaser" in this story has nothing to do with chasing anybody or being chased; it is another euphemism for the deadly poison the hero will probably be using to kill his wife.
Collier is telling a tongue-in-cheek story about love and marriage. He had a cynical attitude towards the subjects, probably because of his personal experience. A more serious assessment of marriage is to be found in Leo Tolstoy's classic story "The Kreutzer Sonata." Both writers thought that people think love will last forever and that most of them find that marriage is disillusining. Here is a pertinent passage from Tolstoy's story:
“We were like two convicts fastened to one chain, hating each other, each poisoning the life of the other and striving not to recognize the fact. I did not then realize that ninety-nine per cent of the married people live in the same hell as mine, and that it must be so. Nor did I then realize that it was so of others or true of myself."
In both Collier's and Tolstoy's stories men end up murdering their wives.