Olivia Hope and Ben Smart disappeared in the Marlborough Sounds in the early hours of New Year's Day in 1998. Investigative journalist and author, Mike White, has covered this case through all its twists and turns over two decades.

Ben Smart and Olivia Hope were last seen about 4am on January 1 1998 when they were dropped off to a yacht by a water taxi.

Ben and Olivia were planning to sleep on the chartered yacht Tamarack but found all the berths were full.

Three other passengers were travelling on the water-taxi, one was a single man who offered the pair a place to sleep on his yacht.

Ben and Olivia head off with the man, to his yacht - this is the last time they are seen alive.

Five months later, on the 15th of June, 1998, Scott Watson was arrested and charged with their murder.

Go to this episode on rnz.co.nz for more details