Shelters a fugitive, e.g

• Shills for, e.g.
• Helps in a bank heist, say
• Renders criminal assistance
• Assists a felon
• Disables the alarm, say
• Helps badly?
• Assists, as with a prison escape
• Assists illicitly
• Helps in wrongdoing

Wiktionary Word definitions in Wiktionary
vb. (en-third-person singular of: abet )