Minors and cofactors

Expand $\begin{vmatrix} 2 & 1 & 0 \\ 1 & 3 & 1 \\ 0 & 1 & 2 \end{vmatrix}$ along row 1 and you get $8$. Along row 2, with the signs $+ - +$: $1(2) - 3(4) + 1(2) = -8$. Same determinant, two answers. Which one went wrong?