Joe is a tall, caucasian American male with bright blue eyes and a mixture of brown. When attending the class reunion, he wears a white blazer and dress pants, along with a dress shirt and dress shoes. Later in flag football, he wears a pair of gym shorts and a white sleeveless shirt with black along the shoulders. A distinguishing characteristic is a tattoo of Jesus Christ on his left pectoral muscle.
Joe Walker grew up a class football star in high school, though he embodied some violent aspects to his personality along the way. Back then he was in a relationship with Janet Walker, somewhat of a friend to Dexter Morgan and he took out his rage by abusing her, often leaving bruises along her arms. Whether it is something she did or just his own frustrations that caused him to hit her, is unclear however based on how he acts now as an adult it is likely him being at a heightened level of frustration that forced her into harm's way.
He admits to Dexter that he has had an attraction to classmate Trisha Billings since they were in high school, asking himself why he hadn't "tapped that". When Dexter informs him that it was because he was already seeing Janet Walker, Joe stares at him with a look that suggests that he believes he could have cheated anyways but decides to "agree" with him nevertheless. This doesn't stop him from an attempt to get in close with her in the present, though it would appear he didn't have much luck (while Dexter himself, did...as unexpected as it was). He later jumps for joy at the possibility of getting a chance to sleep with her when sent a fake text by Dexter in order to lure him into a trap.
Walker enjoys his fame, he cruised on it through high school and expected just as much during their high school reunion. While people did meet and greet him, a hint of jealousy began to form when all the attention swarmed Dexter Morgan due to the success that he's had, how he currently looks compared to his former classmates and other various reasons. Dexter approaches him when given a chance, to which Walker is less than pleased to see him but fakes a greeting to get through this encounter.
When he's asked about Janet and how he feels about her loss, he offers bleak sentiment over his wife...and gives some hints through a slight increase in frustration of what he really feels about her. He states that she never should have left him, but in an angry tone...when in reality this relates to the fact that she sought divorce and likely would have bled him dry of many of his assets. Later on he admits to why he killed Janet and faked it as suicide, that he only sought a way out of divorce...this both infuriates and puzzles Dexter...as to why such a simple disagreement would lead him to killing such a sweet person. It is likely his abuse of her as well as his attitude forced her away and that's why she wanted to escape...he was too blind to realize he was the problem and ended her life out of greed. Finally, when Dexter reveals his tattoo of Jesus Christ on his left pectoral muscle he struggles to find words to describe reasoning behind his actions. Dexter orders him to find a relation to his lord and savior, at first Joe seems a bit dumbfounded...but as his death nears, he advances his love for God and proclaims that "He is a mighty fortress" and nothing can hurt him...which is shortly proved wrong by a sledgehammer to his forehead.
Apart from his personality, he does have some notable qualities in the athletic department. As a football player, he has a muscular physique and is fit to handle lengthy sessions of the sport. He has amazing reflexes as well, being one of very few individuals to ever anticipate Dexter injecting him with a needle...however his fighting abilities are much inferior to Dexter's, who is well-trained in martial arts.
Joe Walker is a former quarterback that went to Dexter's high school back in the 1990s, at the time he dated an associate of Dexter's named Janet McKellin. Janet was a sweet, caring person that looked at Dexter in a way most wouldn't...as a friend. Joe personally barely noticed Dexter's existence and focused more on his football career as well as keep Janet within his tight grip of a controlling relationship. Nevertheless, both of them ended up married shortly after high school and both moved out of state.
Three years before Dexter's 20th high school reunion, Janet Walker was found dead in their house. The police ruled it as suicide however Dexter was skeptical due to dried blood found underneath her fingernails at the time, which could not have been from herself. Considering location differences, Dexter never had an ample time to try and investigate Joe...which is why the 20th high school reunion would work wonders for him. Anticipating his arrival, Dexter prepared a needle to which he could prick a sample of his blood and analyze it back at his lab to match whether or not it was Joe's.
Joe arrives as planned at the reunion, conversing with former students as Dexter expected. However shortly following Dexter's arrival many of his previous classmates start to swarm him, which Joe eventually notices and gives a look of jealousy to losing his fame to someone else. Eventually Dexter gets a chance to walk up to him, intending to shake his hand (which is a trap to prick his blood with a needle somehow fashioned into his class ring) but backfires when he instead uses the greeting of pounding two fists together (which forces Dexter to prick his own hand by mistake). The two converse, with Joe most of the time acting like he wants nothing to do with Dexter...but eventually he recognizes who Dexter is and refers to him as the lab geek in somewhat of a mocking manner while laughing about it. Dexter tries to find out more of his feelings and involvement with Janet (trying to hint at whether or not he killed her), observing a fake set of emotions for missing her...but some intriguing more darker emotions of "her leaving him", though put in the context that she left due to passing away (when in reality, it was going to be divorce). He eventually notices Trisha Billings and stands there next to Dexter, talking about his attraction to her...when he claims he should have tapped that in high school Dexter informs him the reason he didn't was because he was seeing Janet at the time...to which Joe replies with a slight sigh to that kind of mentality and agrees if just to shut him up. He makes his way over to Trisha regardless in an attempt to make up on his desire, though it apparently fails.
Dexter, frustrated that he didn't get his opportunity to test Joe's blood, finds an alternate solution...a nearby signup sheet for flag football suggests him an opportunity to get in close and get another shot. Of course, this requires Dexter to first learn how to play football. Both men do eventually meet on the field along with former classmates and much to Dexter's disappointment, his needle becomes busted and is forced to take...alternate measures. Thanks to advice from Harry, Dexter elbows Walker in the face and uses a towel to dab some of the blood from his nose...succeeding in his mission despite how angry Joe gets.
Later on after Dexter confirms the blood to be a match, he plans how he's going to kill Walker. The original plan was to grab Joe after a couple of drinks and lure him outside where he'd "M99 him", but along his way through the school Trisha Billings arrives to confront him. Displaying an attraction to him during their previous encounter, she walks with him and eventually pulls him into the classroom of one of their teachers. Dexter, who was preoccupied with taking care of Joe, tries to work his way out of it...but as she strips and begins to provide him oral, that plan is put on hold for the moment. After the two finish, he slips her phone out of her purse and uses it as a way to pull Joe under the bleachers.
The plan works and he arrives as planned, though when Dexter attempts to M99 him he is surprised by the quick reflexes that Joe displays, slipping out of the attack to place himself at a vantage point where he can see his attacker. He throws some angry lines at Dexter, wondering what he's doing there and Dexter talks in what must seem like riddles to someone like Joe...who accepts a challenge to fight him. Little does he realize just how combat oriented Dexter is and is quickly overpowered, put in a choke hold and passes out shortly thereafter. When he awakes, he is on Dexter's table...scared and confused like most of his victims, he begs to be let go. The two converse, with Dexter questioning Joe's reason to kill Janet...to which he admits it was simply over divorce. Bewildered, a little angered and somewhat confused, Dexter asks if that was the best reason he could think of for killing someone...to which Joe agrees that was all it was, he was going to end up broke because of it. Dexter, dealing with the question of religion in his mind, reveals the tattoo that Joe has on his chest...and asks him what Jesus would have done, would God have supported this? Joe, now babbling various different excuses, claims that God would forgive him...but not Dexter if he chose to kill him. Of course at this point he is likely stuck between trying to find a way to prevent Dexter from killing him and answering Dexter's inquiry about religion...though as he starts to sound more and more crazy with his speech, Dexter grows tired of it and smashes Joe's skull with a sledge hammer. Likely to insure he's dead...he also brings his blade up and stabs Joe in the heart, as per the normal ritual proceedings.
Joe's body is discarded as normal and due to the fact that he lives in a different state, there isn't much else to worry about regarding his disappearance.