What is the meaning of [The game is afoot]

The phrase ‘the game is afoot’ means ‘the process is underway’; for example, ‘The teams are on the pitch – the whistle blows – the game is afoot.’

The first use of ‘the game is afoot’ is found in Shakespeare’s King Henry IV Part I, 1597:

“Before the game is afoot, thou still let’st slip.”