Help please!!
What effect does Catherine's allusion to the Underground Railroad have on the mood of this passage?

It relaxes the mood by showing how the characters converse.

It lends a more hopeful mood to the scene.

It increases the sense of suspense and fear.

It gives the events an old-fashioned feeling of historical times.

The Shadowland Tunnel

Between the wave-whipped headlands of Dredmor and the sun-brightened hills of Valegreen, the unknown hazards of Shadowland Tunnel beckoned. As the self-driven cart hurtled down the track toward the tunnel entrance, its whistle hooting rudely, Jake and Catherine exchanged looks, trying unsuccessfully to reassure each other.

"No one has ever returned from this tunnel to describe what it's like," Catherine shivered.

“Do you think we should go back?” Jake asked.

“No, the tunnel is our only chance for freedom. We have to be daring enough to take the risk.”

The angle of the track steepened downward as the cart descended toward the gaping pitch-black cavity that was the tunnel’s entrance. Here, the dark green vegetation took on weird tints of purple and crimson, and from somewhere a wind arose, its moans sounding like warnings.

“I feel like we’re heading into the River Styx,” Jake said, his voice trembling. “You know, in Greek mythology, the river of the dead? Like we’re souls who’ve just died and we’re going to meet Charon, the guide, who’s going to ferry us into the underworld.”

“Why are you saying that?” Catherine quailed. “Are you trying to scare me? Maybe the tunnel’s like the Underground Railroad, and it’ll take us to a place where we won’t be hunted anymore, and we won’t be outcasts, and we’ll be free.”

The final syllables of her reply faded at the exact moment when the cart plummeted into the chute that marked the tunnel entrance.

The Underground Railroad was a system of people, routes, and safe houses that enslaved persons used to escape to freedom.