Old Ghost Photo

Riki sent us this old ghost photo which is quite incredible. It has what some call "ghost lightning" in it - we've seen this effect only a few times. How do you explain this anomaly, when it appeared in an old ghost photograph, meaning it was taken with film and not a newer digital camera? (This photo was our ghost picture of the month for September, 2006.)

"Say...I'm thinking this runs in the family! Look at this picture of my great, great grandfather." - Riki