Project Blue Book

Aidan Gillen portrays Dr. Allen Hynek, a highly intelligent astrophysicist who is recruited by the US Air Force to lead the top-secret investigations into UFO sightings. Dr. Hynek is known for his scientific approach and gradually becomes more convinced that there is a government cover-up of extraterrestrial encounters.

Michael Malarkey plays Captain Michael Quinn, a decorated US Air Force officer who partners with Dr. Allen Hynek on the UFO investigations. Captain Quinn is initially skeptical of the unexplained phenomena but gradually develops a close working relationship with Dr. Hynek as they uncover a vast conspiracy.

Laura Mennell portrays Mimi Hynek, the wife of Dr. Allen Hynek. Mimi is a supportive and dedicated partner who navigates the challenges of being married to a scientist involved in secret government work. As the series progresses, Mimi becomes more involved in her husband's investigations.

Ksenia Solo plays Susie Miller, a mysterious and alluring Soviet spy who forms a connection with Dr. Allen Hynek. Susie initially infiltrates the UFO investigation team to gather information but soon finds herself torn between loyalty to her country and her growing feelings for Dr. Hynek.

Neal McDonough portrays General James Harding, a high-ranking US Air Force officer who oversees the Project Blue Book investigations. General Harding is a no-nonsense military man who is determined to keep the truth about UFOs hidden from the public at all costs.

Michael Harney plays General Hugh Valentine, another senior US Air Force officer involved in the Project Blue Book investigations. General Valentine often clashes with Dr. Allen Hynek and Captain Michael Quinn, as he represents the more skeptical and secretive side of the military.

Nicholas Holmes portrays Joel Hynek, the young son of Dr. Allen Hynek. Joel is a curious and intelligent child who becomes fascinated by his father's work on the UFO investigations. He often provides a youthful perspective on the strange occurrences taking place around them.

Deborah Trotchine plays a student who encounters Dr. Allen Hynek during one of his lectures. While her character's name is not specified, she serves as a representation of the general public's interest in and skepticism towards the UFO phenomenon.