"We must shut the trap by hand!" he cried to Andy. "Quick, before that Russian cruiser spots us!"
The chums ran up the ladder to move the door.
But the plate was heavy and ran in a tight groove which was water-proof, and for the minute it refused to budge.
Suddenly a yell came from the deck of the Ivan II.
The Holland had been discovered.
"The accursed American sea-devil!" roared the Russian captain. "If she gets the chance she will sink us as she has sunk the Tien-Tsin and other ships."
He ordered that a bomb be brought on deck with all speed.
This was done, and a few seconds later the deadly thing was hurled straight at the Holland XI.
It struck the open trap-door, bumped on the steps, and rolled at Oscar's feet.
The fuse was burning briskly, and in a few seconds more the bomb would go off, creating destruction and death upon every hand!