This chapter integrates different parts of the book. A general model of motivation involves dopamine underlying the 'wanting' part and opioids the 'liking' part. Humans (and other mammals) appear to strive to maintain their mood within a tolerable zone, if necessary, through addictive activities. A widely observed feature amongst sexual serial killers is an early history of abuse, bullying and taunting. Many killers have failed to develop any bonding with an adult caregiver. High levels of stress are evident throughout their lives. Stressors that seem to carry particular weight are those of humiliation in social interaction, where revenge might seem appropriate. Chronic stressors repeated over years can be distinguished from the acute stressors that often immediately precede a killing. Many heterosexual killers disapproved of what they perceived to be immorality of an important female, such as a mother or wife. Sibling rivalry and excessive drug/alcohol intake characterize some of those described here.