Tied into that doctor's research considering the mass relays I was thinking something like this:
her research leads to some sort of acknowledgement of older races and possibly "Shepard's" reapers.
She stumbles upon the reaper's fallback scenario mass relay now that the Citadel is not an option for them, which happens to be at a location that would lead to Earth becoming the Reaper's bridgehead into counsil space.
The ultimate sacrifice to be made then (after rescuing the good doctor who got abducted in the process) is to let earth indeed take the first blow IF you as Shepard decide that it would be for the greater good instead of allowing the reapers access through the citadel some way.
Dunno... just a shot in the dark there
Modifié par oOmpie, 22 février 2011 - 01:59 .