Cross and Green are forced to defend the displacement beacon against a variety of attacking Xen creatures, including a Manta Ray. In the midst of the battle both characters are caught in what is explained as a "harmonic reflux" by Dr. Keller. It is during this sequence that the voice of Dr. Rosenberg can be heard warning that he "can't keep the portal open much longer," alluding to Calhoun's coinciding trip in Xen during Blue Shift. Dr. Cross and Dr. Green then return safely and Dr. Keller congratulates them on their success.
The resonance reversal presumably had the effect of severely weakening the resonance cascade. It still remains unclear whether the doctors managed to survive the nuclear explosion that occurs at the end of Opposing Force.
