Substitute Andre Ayew scored a second-half equaliser to earn West Ham a Premier League point against Watford.
The hosts went ahead on three minutes through Troy Deeney's penalty after Mauro Zarate was brought down in the box by Cheikhou Kouyate.
Just three minutes later they could have doubled their advantage but M'Baye Niang's powerful drive flew narrowly over the crossbar.
The game was held up for a lengthy period just before half-time when West Ham's Zarate went down with a knee injury. He was taken to hospital for a scan to determine the extent of the problem.