Detectives hope a large offer of cash will prompt someone to reveal exactly what happened to a man they believe was murdered in 1999.
Martin Joyce was last seen by his family when he gave his sister a lift in Manchester, before he went on a night out. Police think he was attacked at a now-closed pub in the Ancoats area of the city.
Officers dug up the Bank of England pub in 2016, looking for remains, but found nothing.
A 64-year-old man was interviewed under caution in March, but no further action was taken.
The lead investigator has questioned how someone "can live with themselves" knowing what happened and not come forward.