They were never seen again.
Leslie's family says just before they disappeared, Leslie was having marital problems.
Could Leslie have taken Julie, 6, and Timmy, 3, and started a new life?
Could they have joined a cult -- something Leslie had been reading into?
ALSO VIEW | Earlier episodes of "Missing" with Kristin Thorne
Could their car have gone off the road and sunk deep to the bottom of one of the many murky bodies of water surrounding her house in Katonah?
Leslie's family and Tim Guthrie Sr., Leslie's husband, have gone in circles for 46 years trying to answer those questions.
WATCH: Kristin Thorne interviews Leslie's family about her disappearance
'Missing:' Mom, 2 children vanish from Westchester in 1977
According to the National Center for Missing and Exploited Children, Leslie Guthrie has a strawberry birthmark on her chin and on her back.
They were last seen driving a green 1974 Ford Maverick with a white roof and the New York State license plate 636-WNA.
Can Eyewitness News investigative reporter Kristin Thorne help the family zero in on one of the theories and lead them to Leslie, Julie and Timmy?
The Bedford Police's Detective Bureau and the National Center for Missing and Exploited Children are working together on the case.
Anyone with information can contact Det. Whalen at 914-241-3111. You can also call in tips to 1-800-THE-LOST.
If you are missing a loved one, you should register them in the National Missing and Unidentified Persons System. You can also look up a missing loved one there.
CREDITS
Kristin Thorne | Writer, Producer, Eyewitness News Investigative Reporter
Emily Hartmann | Senior Digital Producer, Videographer, Editor
Stephen Cioffi | Photographer, Videographer, Editor
Rolando Pujol | EP Digital Content, Innovation, and Strategy
Townsend Davis | Attorney
John Del Giorno | Aerial Photographer
Xizmo Media Productions | Aerial Cinematographer
Brett Cohen | Videographer
Alan Huijsmans | Editor
Yoomi Chong | Creative Director, Design
Joseph Kollar | Graphic Artist
Lori Steinberg | Graphic Artist
Marilu Galvez | President, General Manager
Scott Matthews | News Director
Kim Dillon | Assistant News Director
Peter Kunz | Assistant News Director
Jim Gorham | Vice President, Marketing
Brandon Nelson | Creative Director, Brand
Josh Hartmann | Marketing Producer
Brandon Cook | Media Manager
Omar Rodriguez | Assignment Editor
Sarah Kim | Assignment Editor
Morena Basteiro | Assignment Editor
Robert Monek | EP Web, OTV Digital Project Manager
Katherine Lavacca | Digital Content Producer
Alex George | Desk Assistant
Adrienne Anderson | Sr. Vice President, Content Development, ABC Owned Television Stations
Justin Allen | Executive Producer, Content Development, ABC Owned Television Stations
Rachel Schwartz | Director, Content Operations ABC Owned Television Stations
Luke Richards | Senior Manager, Content Development, Walt Disney Television
Debra OConnell | President, Networks
WABC Television New York, LLC | 2023