Moving around the right side of the basement reveals that a few floorboards are loose.

Extremely suspicious. We should try to pry them up.

Having a crowbar is always a good feeling, but the boards only go up when we stand on them.

You need something that will push down on the floorboards. Something heavy.

You don't need to go far - the item we need is here in the basement.

Something fairly small, but heavy.

It's typically used to knock things over.

The bowling ball on the left can be picked up and used to keep the floorboards propped up.

Note that you need to be standing on the floorboards to interact with them.

Using the crowbar on the floorboards revealed a strange tunnel - and a very suspicious mound of dirt inside.

We should try to dig it up.