G.I. Joe A Real American Hero #13

LAST PLANE FROM RIO LINDOThe surviving Joes hunker down in an abandoned Cobra research station after the skirmish with Cobra in Sierra Gordo, but who will get to them first - the G.I.Joe extraction team or the mercenary groups looking to plunder the outpost?And what is that tapping noise from the blown-up bunker at the bottom of the river?