Slipping a bit as the trail dipped into the saddle of the forgotten church

[sobhan]

Slipping a bit as the trail dipped into the saddle of the forgotten church, Ellen felt the difference without understanding it. The dogs were agitated, their heads low as they tracked an invisible scent and whined low in their throats. They went halfway around the church, then came back at a run, noses snuffling at the base of the broad steps as they crisscrossed each other’s path and fur lifted in strips between their shoulder blades.
What does "Slipping a bit as the trail dipped into the saddle of the forgotten church, Ellen felt the difference without understanding it"
She is climbing up a hill with her dogs.
Source: Redemption Road, John Hart

 

[Keith Bradford]

Ellen was slipping as the path descended into a saddle (geography: a ridge connecting two higher elevations) where the church was. She felt the difference (don't know what this is - presumably referred to in an earlier sentence)...

 

[Thomas Tompion]

Slipping a bit as the trail dipped into the saddle of the forgotten church, Ellen felt the difference without understanding it. The dogs were agitated, their heads low as they tracked an invisible scent and whined low in their throats. They went halfway around the church, then came back at a run, noses snuffling at the base of the broad steps as they crisscrossed each other’s path and fur lifted in strips between their shoulder blades.
What does "Slipping a bit as the trail dipped into the saddle of the forgotten church, Ellen felt the difference without understanding it"
She is climbing up a hill with her dogs.
Source: Redemption Road, John Hart

This is a walk she does frequently. The path goes along a ridge which falls into a flat place (the saddle) where the church stands. The 'difference' is a reference to something which is to come. We don't initially know what this 'difference' is, but the word warns us that something is afoot. Then she finds that the car tracks lead right to the door of the church and that the chains which keep the door shut have been removed - so she knows that something is wrong.