To inject contacts into journey B based on email engagement in journey A, Northern Trail Outfitters should use an engagement split followed by an update contact activity to a Boolean field on an engagement data extension in journey A, and query the engagement data extension for journey B injection. An engagement split is an activity that allows marketers to route contacts based on their engagement with email messages, such as opens or clicks. An update contact activity is an activity that allows marketers to update contact attributes or data extension fields based on journey data. A query activity is an activity that allows marketers to retrieve data from data extensions using SQL queries. Reference: https://help.salesforce.com/s/articleView?id=sf.mc_jb_engagement_split.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.mc_jb_update_contact_activity.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.mc_as_query_activity.htm&type=5