This helps create sympathy for Karl and also paints a clear picture of Karl's past. Once Karl and Frank meet, they are almost inseparable (the exception being when Karl has to work). As the movie progresses, their relationship grows. For both, it is their first real friendship. Karl is a role model for Frank and is always correcting him when he curses and stating, "you are too young to hear bad things". Karl relates to Frank since they both went through a lot at a young age. Frank, in return, relates to Karl because he realizes Karl understands how he feels. Karl is also like a safe haven to him from the scary world in which he lives. This unusually relationship is one of the most sincere and loving relationships throughout the whole movie.
At the same time Karl and Frank's relationship is growing, Karl and Linda's relationship begins to blossom. Linda knows that Karl was hospitalized but thinks it is because Karl is slightly retarded. Linda sympathizes with Karl, which is why she embraces him into their small family. Linda realizes that Karl is a good companion for Frank and shows nothing but compassion and love for him. Even when Linda finds out the truth about the hospitalization, she retains her faith in Karl and agrees when he reassures her that he would never hurt her or "the boy". Karl knows Linda is a good mother and their relationship is similar to a parent-child relationship. He does not blame Linda for being in an abusive relationship and instead does everything in his power to protect her and Frank. Unfortunately, to Karl this means another killing.
Doyle is the abusive boyfriend of Linda. He is the stereotypical male. He is an ineffective listener, rarely expresses his emotions (except for anger), and has little sensitivity to others (all of these qualities are found in The Power to Communicate by Borisoff and Merrill). He verbally and physically abuses Linda and verbally abuses Frank, Karl and Linda's gay friend, Vaughn.
