Possible Clues:

• 55 in river search
• Dig for Victory in Europe after Adele is shelled
• Limitations to dialogue, as it happens, precluding one search
• Rummage among model vegetables
• Dig into strudel, Vera!
• Go deeply inside model — very deficient
• Investigate, with ''into''
• Research (into)
• Burrow (into)
• Conduct an exhaustive probe