What Makes a doubter become a martyr?

One of the interesting places we got to visit on this trip to India, was St. Thomas' mount. It is a small hill, where it is said that Doubting Thomas was martyred. Thomas arrived in southern India in A.D. 52 and was martyred with a lance through his back, while in prayer (in A.D. 72). The striking image is in the entrance to the small church on the top of the hill. On the left side is a caricature of Thomas reaching up his hands toward the scars in Jesus' hands and sides. On the other, Thomas is kneeling in prayer with a lance about to be speared through his back.

What makes a doubter become a martyr?
What makes a doubter travel over 3000 miles from home, to a completely foreign land to tell the good news about the scarred risen Savior?

The one who asked, "Lord, how will we know the way?" (John 14) now knows for sure that Jesus is indeed, the way, the truth and the life (John 14:6)

Maybe Doubt isn't such a bad thing...

Coincidently, I find it ironic that the following sign was stationed near the entrance to the Mount: