était. ..marcha. Notice the tenses, E.B

1. 26. en tiers. In this phrase and in un tiers, the word tiers generally indicates that the person in question is more or less out of place in the company of the other two. It is not exactly a synonym for troisième, but is limited to the above use, and to certain phrases, as le tiers étal (the Third Estate), une fièvre tierce (a tertian fever).