Episode 9
S4, E9: When a spell cast by Willow goes awry, Buffy vows to marry Spike, Giles loses his sight, and Xander attracts an overabundance of demons.

S4, E9: When a spell cast by Willow goes awry, Buffy vows to marry Spike, Giles loses his sight, and Xander attracts an overabundance of demons.