Escaping the Prison
He appears alongside another officer to notify Henry that he's "free to go", but he was joking and he started laughing at Henry for falling to his joke. They came to deliver him a package, claiming that Dave already checked the package for anything "useful" (to help Henry escape); but Dave, however, forgot to check the package before giving it to Henry. He lies by assuring that he did, for not wanting to "lose [his] job". When Dave goes away with his partner, Henry finds a cake, and inside, a truly helpful tool (depending on player's choice) which lets Henry escape. He was later fired.
Stealing the Diamond
When he got fired from the police, he found his new job as a night security guard in the museum targeted by Henry in his attempt to steal the Tunisian Diamond. He was set to guard the World War II section. When Henry demolished the wall with a pick, Dave started telling a security guard holding a revolver about the events of Henry's escape. Then, Henry throws a model airplane to the security guard's head and Dave starts running away to get help. He crashes into a column and knocks himself out.
Infiltrating the Airship
After events of Stealing the Diamond, Dave somehow got captured by the Toppat Clan, an organization of criminals. They then took him into their airship and locked him into a cell next to the vault area. A key that opens his cell was left next to the Toppat computer. Henry has the option to pick it up. If he does, later he frees him. Dave flees and manages to get inside the vault. He falls from the ceiling, but survives and runs away.
The airship later crashes because Henry steals a Ruby from the vault. This leads to a huge chaos in which many Toppat members and (possibly) prisoners are killed. Dave's fate was not revealed.
In any other ending, Dave remains locked in his cell, and his ultimate fate is unknown.
Dave seems to be a forgetful person since he forgot to check the package before giving it to Henry. He also lied about having to do so, for not wanting to "lose [his] job".
- If Dave didn't lie about checking Henry's package, they would probably check it again and find tools inside it, so Henry would never escape the prison, and next games, like Stealing the Diamond, or Infiltrating the Airship wouldn't exist.