The doctor glanced back and forth.
'The senior immortals are housed in the third row.'
'Right!' Tom brandished his knife. 'I'll take the left side. You take the right. When we've finished we'll move onto the other rows ...'
'Couldn't we just blast them away?'
'No.' Tom shook his head. 'I've done a study of this place. Ray guns won't operate here. We'll have to take them out one-by-one ... there's no other way.'
They set off down the row, exterminating the immortals.
'Abu ... Abu ... Yea ... Yea ...'
The groaning became increasingly erratic. Tom was reminded of a computer with disintegrating memory chips. The dying immortals were a bit like computer chips. Sooner or later Big Brain would shut down completely.
They reached the end of the third row and were proceeding to the fourth when a colossal thump caused the floor to shake. Jars toppled from their stands. Another thump followed. There could be only one explanation. The massive steel and concrete doors, which were the Forbidden Zones ultimate defence, had come crashing down. They were locked in.