When Mindy Stern and her husband returned home from a weekend trip and found a wet envelope on their doorstep, they knew who had left it there: their cat, Nile.

Nile may bring home an occasional mouse or two, as any typical outdoor cat would do, but his most frequent offerings are paper items and litter: a library overdue notice, a business advertisement, a University of Washington parking stub.

The envelope, it turned out, contained a card of congratulations for a couple’s wedding.

“When I saw the wedding card signed ‘Mazel Tov,’ I knew it was important — it was a beautiful card and would be a shame for it to just get lost,” Stern said.

After some research, Stern found that the card had accompanied a wedding present delivered to the home of Maxine Schnebele, on the street below Stern’s house. The card had somehow gotten dropped.

The two neighbors met for the first time when Stern brought over the wedding card. They discovered that they had both been living in the same neighborhood for over a dozen years. They also found that they are both Jewish, and they began corresponding by e-mail.

Schnebele wanted to see Nile, so a couple of days later, Stern packed the 16-pound tabby cat into a bag and toted him down the narrow, steep trail behind her house that connects to the street below. He patiently endured the short trek until arriving at the neighbors’ doorstep; as the Schnebeles answered the door, he made an escape — allowing them only a glimpse — and headed for home.

Nile, now 14 years old, was a feral cat during the first year of his life. When Stern’s husband, Shlomo Freiman, was working at the Bellevue Humane Society, the staff there knew that the couple was looking for a cat.

“The girls knew when Nile came in — they said, we have the perfect cat for you,” said Stern.

Nile was the couple’s first rescued pet. They now have three: a Jack Russell terrier, a Cairn terrier and another cat named Sid. The terriers go to work with Freiman, who manages his own veterinary practice: the Animal Hospital of Factoria. The couple also has two grown sons.

Nile spends his days roaming the neighborhood and his nights sleeping soundly in Stern’s garage, which has a kitty door.

“Keeping him indoors has been a challenge — he likes to escape. He’s happy outside,” said Stern, who is a social worker at the University of Washington. “On a daily basis, he picks up plastic bags — like someone went to Subway and ate their lunch, and threw away the paper. He picks up litter … sometimes, he deposits envelopes with mail. He put an envelope on the front doorstep that looked like it was important — like it was from a bank … I put a sticky note on it and delivered it to the neighbors whose address it was intended for. The next day, (Nile) returned it to us with the sticky note still on it,” said Stern.

As for the name “Nile,” Stern chose it, she said, because cats came from Egypt. The Nile River was the inspiration. “He’s the friendliest and gentlest cat we’ve ever known,” she said.

Perhaps too friendly, at times; he has gotten himself adopted by other neighbors in the past. “He just goes up to people and snuggles with them — curls up on their couches,” said Stern. In fact, when the next-door neighbors moved away, they were “heartbroken about leaving their two surrogate children”: Nile and his buddy, Sid, who tends to tag along.

Stern doesn’t worry about the pair, even though Nile has been in a few tussles with raccoons. “He knows how to stand his ground,” she said.