A three-legged hero dog battling cancer rescued a struggling week-old otter adrift in a frigid Minnesota river without its mother.

In February, Gus, a six-year-old Goldendoodle, lost his leg to amputation after being diagnosed with a cancerous tumor, KMSP-TV reported. He continues to receive chemotherapy treatments at the University of Minnesota Veterinary Hospital, but he is as active as ever.

“We thought, ‘Oh this is going to be so sad; he isn’t going to be able to run again like he used to,’ but this hasn’t slowed him down at all,” Gus’s owner, Cleo Young, told WCCO.

On Easter Sunday, the pooch was spending time with Young’s granddaughters Ella and Lucy Hammerstand as they did chores on the shores of the St. Croix River in Lakeland, Minnesota, according to KMSP. Suddenly, the Goldendoodle waded into the frigid water, causing concern among the two girls who were unsure if he could still swim. Gus swam about fifty feet out into the river before returning to shore and placing the otter pup at Ella’s and Lucy’s feet, according to WCCO.

“First time swimming with three legs and he comes out of the water with a baby otter in his mouth!” Ella told KMSP-TV.

“I held him for a little while they tried to find his mom, but we couldn’t,” Lucy said.

The family swaddled the animal in towels and hurried him to the nonprofit organization Wildlife Rehabilitation Center (WRC) of Minnesota in Roseville, according to KMSP-TV.

“It was kind of a harrowing trip because it was closing at 6 p.m., and we didn’t know if we were going to make it,” Young told WCCO.

The family arrived before closing and turned the otter pup over to the WRC.

“The otter is much too young to be in the water — it should still be in the den with its mom,” the WRC explained in a Facebook post. “Having no idea where the den is, how far the little guy traveled, the otter has been admitted for rehabilitation.”

After concerns about the animal’s condition for about the first 36 hours, the pup “turned the corner” and showed signs of improvement, according to the post. The otter, estimated to be a week old is now in the care of a different rehab facility with specialized pools that aid in raising otter pups, KMSP-TV said.

“Kudos to Gus, and his wonderful owners Cleo and John, for saving this young otter’s life,” the nonprofit said.