Henry's family takes in a stray cat, the ugliest cat they have ever seen, and an amazing relationship blossoms between it and their big dog Mudge.

Follows the seaside adventures of Henry, Henry's father, and Henry's big dog Mudge.

At first Henry's very neat cousin doesn't like the cookies from under his bed or Mudge's slobbery kisses, but when they all play frisbee, she begins to enjoy her visit.

For Henry and his big dog Mudge, spring means admiring the first snow glory, playing in puddles in the rain, and watching the five new kittens next door.

While trying out the spy glasses, spy hat, and other items in their new spy kit, seven-year-old Henry and his dog Mudge make a new friend and form a spy club.

While Henry's parents are at a Sweetheart Dance on Valentine's Day, he and his dog Mudge have a wonderful time staying at Mrs. Hopper's house, where they enjoy tea and music and dressing up in various costumes.

When Henry's cousin Annie prepares to move in next door he and Mudge help calm her fears.

While trying out the spy glasses, spy hat, and other items in their new spy kit, seven-year-old Henry and his dog Mudge make a new friend and form a spy club.

Mudge looks forward to the Mother's Day surprise that Henry and his father cook up for Henry's mother.

Henry, his parents, and his dog Mudge take a vacation out West, where they enjoy tumbleweeds, desert animals, souvenirs, and the wide open spaces.