EVERETT — The Mill Creek couple had their suspicions.

The summer before last, they’d agreed to help out some old friends.

The friends’ son was dropping out of college in Michigan and starting a new job in Seattle. He needed a place to stay.

For months, he came and went from their home as if he were going to work. He said he was active in church and also spent a lot of time playing on his computer.

Then local and federal law enforcement showed up.

Caleb Dierlam, 20, was arrested Wednesday. He is suspected of bank robberies in Everett, Lynnwood and Mount Vernon.

Prosecutors say the money has not been recovered.

Dierlam remains at the Snohomish County Jail. Bail was set Thursday at $150,000.

Dierlam has no criminal history, according to his public defender.

In Lynnwood in July, a bank teller was passed a note asking her to stay quiet and leave any dye packs out of the cash.

A similar holdup was reported in Everett in August. The next month, Mount Vernon police sent a press release about a bank robbery that appeared to match the others.

Investigators attempted to identify the man with facial recognition software and by releasing surveillance stills and video to the public.

On Dec. 1, a customer at a Lynnwood Starbucks called 911. The customer said a man using a laptop in the coffee shop looked like the robbery suspect from the news. Police learned the man’s name and took his picture, but he was not arrested.

Then they checked out his address and background. He had no employment records in Washington, according to the report.

The FBI contacted Dierlam’s landlords on Monday. His rent was never more than $125 a month, the agents were told.

Not long before the visit, the couple who owned the home learned Dierlam had been lying to them, they said. They believed he was active in church and twice-weekly Bible study groups until people from those groups told them otherwise.

They had confronted him, and he allegedly said he wanted to do the church activities but he was too anxious and he didn’t want to disappoint them.

The couple reportedly said Dierlam’s clothing and mannerisms matched the suspects seen on surveillance footage from the local robberies.

Search warrants were served this week on their home and Dierlam’s car. Detectives allegedly collected clothing and makeup as potential evidence. Dierlam declined to answer their questions.

Criminal justice experts say that hitting a bank is often a desperate act prompted by an addiction, such as gambling or drugs, or a sudden change in lifestyle.

Dierlam’s arrest report made no mention of a possible motive.

Rikki King: 425-339-3449; rking@heraldnet.com; Twitter: @rikkiking.