Watford have sold Dodi Lukebakio to Hertha Berlin for a reported £20m, despite the striker only playing a total of 15 minutes for the Hornets.
The 21-year-old Belgian joined Watford from Anderlecht in January 2018 and was a substitute in a 2-0 Premier League defeat at West Ham the following month.
He spent last season on loan with Bundesliga side Fortuna Dusseldorf, scoring 14 goals in 34 games.
That included a hat-trick in a 3-3 draw with Bayern Munich in November.
The Belgium Under-21 international is the only player to ever score three goals in a Bundesliga game against Manuel Neuer.
“Hertha is a big club in Germany and showed a lot of interest in me,” said Lukebakio after signing what his new club call a long-term deal.
“I knew very quickly that I wanted to join the club. I want to play a lot of football here and score loads of goals.”