15 - Trace of Memory by Keith Laumer

In a desperate search for a way to Miami, Legion finds himself homeless and hungry until he encounters Foster. Foster enlists Legions help to confront the enigmatic light-beings known as Hunters, who have been relentlessly pursuing him, and to recover his fragmented memories. Armed with a centuries-old journal filled with cryptic entries, Foster holds the key to unraveling his true identity. Their thrilling journey takes them from the ancient stones of Stonehenge to alien spacecraft, distant planets, and extraordinary methods of navigating the complexities of age and memory. - Summary by Nick Bulka