Dateline Episode Trailer: A Promise to Helene | Dateline NBC

When college student Helene Pruszynski is found murdered, her case remains cold for nearly 40 years until a new detective uses an innovative method to catch the killer. Josh Mankiewicz reports. Watch this full episode: https://www.nbc.com/dateline/video/a-... Like us on Facebook:   / datelinenbc   Follow us on Twitter:   / datelinenbc   Follow us on Instagram:   / datelinenbc   Plus! Stream recent and classic episodes of Dateline now on Peacock, the new free streaming service from NBCUniversal here: https://www.peacocktv.com/watch/home