In the book "Straight" by Dick Francis, the author explores themes of trust and betrayal through the lens of friendship. An essential quote from the story states that "infinite sadness is not to trust an old friend." This emphasizes the deep emotional impact that comes when one feels unable to rely on someone they once considered close. The sentiment illustrates how fragile relationships can be, and how betrayal can lead to profound sorrow.

As the narrative unfolds, it showcases the complexities of human connections, stressing that losing faith in an old friend can lead to a sense of profound loss. Trust is portrayed as a vital component of friendships, and the inability to maintain it can lead to a cycle of despair. Francis effectively delves into the emotional landscape surrounding relationships, highlighting not just the pain of betrayal, but also the nostalgia of happier times shared with a trusted friend.