Soon after "Apollo" returns to Atlantis, the Asurans retaliate by launching a Stargate satellite that fires an energy beam, disabling the Apollo before zeroing in on Atlantis. The beam will deplete the city's shield in just under 30 hours, and with the satellite and its active Stargate over the city, the Expedition cannot evacuate using their own Stargate. McKay (David Hewlett) and Zelenka (David Nykl) submerge the city to mitigate the effect of the beam, but this only buys them nine more hours before the city is destroyed.