Adiós Chile, Olá Portugal! 'Amazing Race' Contestant Suffers 'Brainfart' [Exclusive Video]

Emmy Award nominee Phil Keoghan, host of Season 21 of "The Amazing Race," premiering Sunday, 9/30 at 8 PM on CBS.

In this exclusive clip from the next episode of "The Amazing Race," it appears that our travelers have landed in Europe for the third leg. And much as with the race to be the first person to sail around the world while building an empire for their homeland and mapping uncharted territories, Portugal and Magellan will play significant roles in this race as well. 

[Related: 'Amazing Race' Screen-cap: Mining, Shining, and Whining]

The Oklahoma oilers, Tim and Danny, seem to be all alone at the Discoveries Monument in Lisbon trying to calculate with a giant compass and an in–ground map the total number of nautical miles that Magellan sailed. It is unclear from the video whether they beat other teams to a Detour or are the last team left at the challenge. Considering that Tim has a self-described "brainfart" in which he forgets that the Earth is round and the stone-faced man in the 16th-century garb rips up their first guess of 1,625, they'd better hope that it's not the latter. Judging by their fairly calm demeanor and lack of pit stains, it's the former.

Tune in Sunday to CBS at 8 p.m. to find out if these best friends will be the next contestants whose "Amazing Race" journey is doomed by math.