Christopher “Chris” Sylvia, a 28-year-old American, is the first of the three missing PCT hikers whose case author Andrea Lankford investigates. He vanished in February 2015, shortly after starting a solo section of the trail near Warner Springs, California. His case, which predated the rise of large-scale, Facebook-enabled volunteer searches, serves as the book’s inciting incident, launching Lankford’s multi-year investigation. The strange circumstances of his disappearance, including a collection of gear found abandoned on the trail, make his story a strong study in clue interpretation. The case also demonstrates the difficulty of distinguishing between a voluntary disappearance and an accident, given the lack of a body or other conclusive evidence.

Lankford uses Chris’s case to explore the cultural phenomenon of escape and wanderlust, and the impact of a hiker’s psychological state on their likely actions. As a result, Chris’s abandoned gear (particularly his copy of Hermann Hesse’s novel Siddhartha) becomes a central investigative thread in the book, as potential insight into his state of mind. Chris’s case conveys the deep strain and confusion that families experience when faced with conflicting leads and unresolved questions. Lankford details how his friends and family grapple with the possibility that he chose to walk away from his life, a hypothesis that complicates the search effort. He defines Lankford’s concluding philosophy that closure means embracing the unknowable.

David O’Sullivan, a 25-year-old Irish citizen, is the second of the book’s three central missing hikers. A recent university graduate and inexperienced hiker, he vanished in April 2017 while hiking through the San Jacinto Mountains in Southern California. His disappearance occurred during a year of record snowfall, a factor that introduced unexpected and severe early-season hazards for northbound PCT hikers. David’s case becomes the primary vehicle through which Lankford dissects official SAR doctrine, the reliability of witness statements, and the emergence of new search technologies like drones and crowdsourced image analysis.

As a novice hiker climbing in poor conditions, David’s case is, in practice, the simplest of the three, pointing to accidental death. His story highlights the critical decision-making points that novice hikers face and how those choices shape the subsequent search areas. His last confirmed contact point and the specific set of hazards he faced—including ice, navigational challenges, and the choice to “flip-flop” or skip a section—exemplify the dangers that hikers (and searchers) must consider. His experience illustrates how quickly a hiker can vanish, leaving behind a complex puzzle for investigators to solve.

David’s case is mainly used by Lankford to portray the immense personal costs of ambiguous loss to the missing person’s family. Through the close involvement of his parents in the SAR effort, including them seeking alternative (and possibly fraudulent) help in locating David, the book explores the vulnerability of grieving families and the ethics of SAR practice.

Kris “Sherpa” Fowler, a 34-year-old hiker from Ohio, is one of the three central missing persons in Trail of the Lost. An experienced long-distance hiker, he disappeared in October 2016 while nearing the end of his PCT thru-hike, last seen at White Pass, Washington, just as a major storm cycle hit the Cascade Mountains. His case is significant for its perplexing nature and for the massive search it inspired, which became one of the largest volunteer mobilizations in the trail’s history and helped catalyze the creation of the Fowler-O’Sullivan Foundation.

Kris’s disappearance helps Lankford explore the inherent risks of long-distance hiking, even for a well-prepared individual, and the challenges of SAR. Vanishing just a few hundred miles from the northern terminus, Kris’s story demonstrates the narrow margins between safety and disaster in the remote wilderness of the Cascades. His established Last Known Point (LKP) and the severe weather context provide a clear starting point for search planners, yet the failure to find him underscores the immense challenge of locating a missing person in such vast and rugged terrain.

Kris’s case provides the narrative with its primary emotional engine and sense of momentum. His disappearance galvanizes his stepmother, Sally Fowler, into becoming a formidable community organizer, and her efforts rally a large online and field-based community dedicated to bringing him home. This collective effort sustains the book’s momentum and illustrates the power of communal care in the face of tragedy. His legacy extends beyond the search itself into the Fowler-O’Sullivan Foundation. Named in his honor, this foundation translates the personal loss of his disappearance into the effort for institutional change and support, and is a key part of Lankford’s argument for a continued, incremental progression in SAR practice.

Cathy Tarr is a key figure in Trail of the Lost. A retired corporate pharmacy manager, Tarr transitioned into a full-time volunteer search coordinator and family liaison after becoming involved in the search for Kris Fowler and David Sullivan. In 2020, she founded the Fowler-O’Sullivan Foundation (FOF) to institutionalize this support for families of the missing.

Cathy’s work is central to the book’s exploration of how dedicated amateurs can effectively organize and professionalize search efforts after official agencies have suspended their operations. Lankford uses Cathy to embody the rise of disciplined, citizen-led search-and-rescue (SAR) in the digital age. Cathy’s methodical approach integrates modern tools like drones, open-source intelligence (OSINT), and systematic image analysis (“squinting”) into her search planning. She develops family-first processes, acting as a crucial liaison who provides vetted resources and shields families from the stress of managing a search. Her work demonstrates a model that successfully blends evidence-based rigor with compassionate care. Cathy is also shown as a key support for the emotional well-being of the families and her volunteer teams. Lankford presents her as an archetypal, protective mother figure whose fellow-maternal feelings drive her compassion and action for the families.

Sally Guyton Fowler, the stepmother of missing hiker Kris Fowler, became a leading figure in family-led advocacy following her stepson’s disappearance in 2016. A business professional from Ohio, she created and managed the “Bring Kris Fowler/Sherpa Home” Facebook group, which became one of the first large-scale, social media-driven efforts to find a missing PCT hiker. Her story highlights the crucial role that determined family members can play in mobilizing resources and sustaining a search long after official efforts have ceased. Sally provides a humane and relatable anchor for the reader, representing the human purpose and meaning that drives the SAR.

Morgan Clements is an OSINT and mapping analyst, the founder of GlobalIncidentMap.com, a firm that tracks and maps global events. In Trail of the Lost, he applies his professional skills in geospatial analysis and data forensics pro bono to the missing hiker cases. Clements represents the maturation of post-9/11 intelligence-gathering techniques and their application in civilian contexts, bringing a new level of rigor to the search for Kris Fowler and David O’Sullivan. His primary contribution to the search is translating vast amounts of raw data—from social media traces and witness reports to drone imagery—into actionable search leads using established investigative procedures. Clements’s work underscores the book’s core argument that verifiable data and systematic rigor are essential in modern search-and-rescue, providing a crucial counterpoint to rumor and unvalidated speculation.

Jon King, known to the hiking community as “SanJacJon,” is an Idyllwild-based mountaineer, wildlife biologist, and the publisher of the San Jacinto Trail Report. He is a well-known local guide and expert who documents trail conditions on a near-daily basis. Jon provided real-time intelligence for the search for David O’Sullivan. In Trail of the Lost, King exemplifies the value of deep, regional expertise and civic-minded volunteerism in search-and-rescue (SAR) operations. His skill, local knowledge, and methodology, based on direct and frequent observation, model the importance of reliable local knowledge. King’s work contributes to the book’s argument for proactive prevention in SAR; his detailed reporting is commended by Lankford for aiding the search for O’Sullivan and educating future hikers, potentially preventing similar tragedies.

Pam Coronado is an “intuitive consultant” psychic and certified SAR volunteer whose involvement in the cases highlights the ethical complexities and varying methodological approaches of modern missing-person investigations. Pam is a self-described “psychic detective” with experience on high-profile missing-person cases, including helping law enforcement. Lankford uses Pam’s involvement to explore the appeal of paranormal or intuitive approaches and the tension between hope and evidentiary standards. Her methodology, which combines fieldwork with intuitive feelings, contrasts with the book’s emphasis on verifiable, data-driven searching. Pam’s involvement prompts Lankford’s critical discussion about whether such leads help, harm, or distract families grappling with ambiguous loss.